--- a/browser/installer/windows/nsis/installer.nsi
+++ b/browser/installer/windows/nsis/installer.nsi
@@ -382,58 +382,22 @@ Section "-Application" APP_IDX
                                  "${AppRegName} Document" ""
   ${AddDisabledDDEHandlerValues} "FirefoxURL-$AppUserModelID" "$2" "$8,1" \
                                  "${AppRegName} URL" "true"
 
   ; For pre win8, the following keys should only be set if we can write to HKLM.
   ; For post win8, the keys below can be set in HKCU if needed.
   ${If} $TmpVal == "HKLM"
     ; Set the Start Menu Internet and Registered App HKLM registry keys.
-    ; If we're upgrading an existing install, replacing the old registry entries
-    ; (without a path hash) would cause the default browser to be reset.
-    ReadRegStr $0 HKLM "Software\Clients\StartMenuInternet\FIREFOX.EXE\DefaultIcon" ""
-    StrCpy $0 $0 -2
-    ${If} $0 != "$INSTDIR\${FileMainEXE}"
-      ${SetStartMenuInternet} "HKLM"
-      ${FixShellIconHandler} "HKLM"
-    ${EndIf}
-
-    ; If we are writing to HKLM and create either the desktop or start menu
-    ; shortcuts set IconsVisible to 1 otherwise to 0.
-    ; Taskbar shortcuts imply having a start menu shortcut.
-    StrCpy $0 "Software\Clients\StartMenuInternet\${AppRegName}-$AppUserModelID\InstallInfo"
-    ${If} $AddDesktopSC == 1
-    ${OrIf} $AddStartMenuSC == 1
-    ${OrIf} $AddTaskbarSC == 1
-      WriteRegDWORD HKLM "$0" "IconsVisible" 1
-    ${Else}
-      WriteRegDWORD HKLM "$0" "IconsVisible" 0
-    ${EndIf}
+    ${SetStartMenuInternet} "HKLM"
+    ${FixShellIconHandler} "HKLM"
   ${ElseIf} ${AtLeastWin8}
     ; Set the Start Menu Internet and Registered App HKCU registry keys.
-    ; If we're upgrading an existing install, replacing the old registry entries
-    ; (without a path hash) would cause the default browser to be reset.
-    ReadRegStr $0 HKCU "Software\Clients\StartMenuInternet\FIREFOX.EXE\DefaultIcon" ""
-    StrCpy $0 $0 -2
-    ${If} $0 != "$INSTDIR\${FileMainEXE}"
-      ${SetStartMenuInternet} "HKCU"
-      ${FixShellIconHandler} "HKCU"
-    ${EndIf}
-
-    ; If we create either the desktop or start menu shortcuts, then
-    ; set IconsVisible to 1 otherwise to 0.
-    ; Taskbar shortcuts imply having a start menu shortcut.
-    StrCpy $0 "Software\Clients\StartMenuInternet\${AppRegName}-$AppUserModelID\InstallInfo"
-    ${If} $AddDesktopSC == 1
-    ${OrIf} $AddStartMenuSC == 1
-    ${OrIf} $AddTaskbarSC == 1
-      WriteRegDWORD HKCU "$0" "IconsVisible" 1
-    ${Else}
-      WriteRegDWORD HKCU "$0" "IconsVisible" 0
-    ${EndIf}
+    ${SetStartMenuInternet} "HKCU"
+    ${FixShellIconHandler} "HKCU"
   ${EndIf}
 
 !ifdef MOZ_MAINTENANCE_SERVICE
   ; If the maintenance service page was displayed then a value was already
   ; explicitly selected for installing the maintenance service and
   ; and so InstallMaintenanceService will already be 0 or 1.
   ; If the maintenance service page was not displayed then
   ; InstallMaintenanceService will be equal to "".

--- a/browser/installer/windows/nsis/shared.nsh
+++ b/browser/installer/windows/nsis/shared.nsh
@@ -145,27 +145,30 @@
 !macro SetAsDefaultAppGlobal
   ${RemoveDeprecatedKeys} ; Does not use SHCTX
 
   SetShellVarContext all      ; Set SHCTX to all users (e.g. HKLM)
   ${SetHandlers} ; Uses SHCTX
   ${SetStartMenuInternet} "HKLM"
   ${FixShellIconHandler} "HKLM"
   ${ShowShortcuts}
-  ${StrFilter} "${FileMainEXE}" "+" "" "" $R9
-  WriteRegStr HKLM "Software\Clients\StartMenuInternet" "" "$R9-$AppUserModelID"
 !macroend
 !define SetAsDefaultAppGlobal "!insertmacro SetAsDefaultAppGlobal"
 
 ; Removes shortcuts for this installation. This should also remove the
 ; application from Open With for the file types the application handles
 ; (bug 370480).
 !macro HideShortcuts
-  ${StrFilter} "${FileMainEXE}" "+" "" "" $0
-  StrCpy $R1 "Software\Clients\StartMenuInternet\$0\InstallInfo"
+  ; Find the correct registry path to clear IconsVisible.
+  StrCpy $R1 "Software\Clients\StartMenuInternet\${AppRegName}-$AppUserModelID\InstallInfo"
+  ReadRegDWORD $0 HKLM "$R1" "ShowIconsCommand"
+  ${If} ${Errors}
+    ${StrFilter} "${FileMainEXE}" "+" "" "" $0
+    StrCpy $R1 "Software\Clients\StartMenuInternet\$0\InstallInfo"
+  ${EndIf}
   WriteRegDWORD HKLM "$R1" "IconsVisible" 0
   ${If} ${AtLeastWin8}
     WriteRegDWORD HKCU "$R1" "IconsVisible" 0
   ${EndIf}
 
   SetShellVarContext all  ; Set $DESKTOP to All Users
   ${Unless} ${FileExists} "$DESKTOP\${BrandFullName}.lnk"
     SetShellVarContext current  ; Set $DESKTOP to the current user's desktop
@@ -216,17 +219,23 @@
     ${EndIf}
   ${EndIf}
 !macroend
 !define HideShortcuts "!insertmacro HideShortcuts"
 
 ; Adds shortcuts for this installation. This should also add the application
 ; to Open With for the file types the application handles (bug 370480).
 !macro ShowShortcuts
+  ; Find the correct registry path to set IconsVisible.
   StrCpy $R1 "Software\Clients\StartMenuInternet\${AppRegName}-$AppUserModelID\InstallInfo"
+  ReadRegDWORD $0 HKLM "$R1" "ShowIconsCommand"
+  ${If} ${Errors}
+    ${StrFilter} "${FileMainEXE}" "+" "" "" $0
+    StrCpy $R1 "Software\Clients\StartMenuInternet\$0\InstallInfo"
+  ${EndIf}
   WriteRegDWORD HKLM "$R1" "IconsVisible" 1
   ${If} ${AtLeastWin8}
     WriteRegDWORD HKCU "$R1" "IconsVisible" 1
   ${EndIf}
 
   SetShellVarContext all  ; Set $DESKTOP to All Users
   ${Unless} ${FileExists} "$DESKTOP\${BrandFullName}.lnk"
     CreateShortCut "$DESKTOP\${BrandFullName}.lnk" "$INSTDIR\${FileMainEXE}"
@@ -287,78 +296,87 @@
     ${If} ${FileExists} "$QUICKLAUNCH\${BrandFullName}.lnk"
       ShellLink::SetShortCutWorkingDirectory "$QUICKLAUNCH\${BrandFullName}.lnk" \
                                              "$INSTDIR"
     ${EndIf}
   ${EndUnless}
 !macroend
 !define ShowShortcuts "!insertmacro ShowShortcuts"
 
-!macro AddAssociationIfNoneExist FILE_TYPE
+!macro AddAssociationIfNoneExist FILE_TYPE KEY
   ClearErrors
   EnumRegKey $7 HKCR "${FILE_TYPE}" 0
   ${If} ${Errors}
-    WriteRegStr SHCTX "SOFTWARE\Classes\${FILE_TYPE}"  "" "FirefoxHTML-$AppUserModelID"
+    WriteRegStr SHCTX "SOFTWARE\Classes\${FILE_TYPE}"  "" ${KEY}
   ${EndIf}
-  WriteRegStr SHCTX "SOFTWARE\Classes\${FILE_TYPE}\OpenWithProgids" "FirefoxHTML-$AppUserModelID" ""
+  WriteRegStr SHCTX "SOFTWARE\Classes\${FILE_TYPE}\OpenWithProgids" ${KEY} ""
 !macroend
 !define AddAssociationIfNoneExist "!insertmacro AddAssociationIfNoneExist"
 
 ; Adds the protocol and file handler registry entries for making Firefox the
 ; default handler (uses SHCTX).
 !macro SetHandlers
   ${GetLongPath} "$INSTDIR\${FileMainEXE}" $8
 
+  ; See if we're using path hash suffixed registry keys for this install.
+  StrCpy $5 ""
+  ${StrFilter} "${FileMainEXE}" "+" "" "" $2
+  ReadRegStr $0 SHCTX "Software\Clients\StartMenuInternet\$2\DefaultIcon" ""
+  StrCpy $0 $0 -2
+  ${If} $0 != $8
+    StrCpy $5 "-$AppUserModelID"
+  ${EndIf}
+
   StrCpy $0 "SOFTWARE\Classes"
   StrCpy $2 "$\"$8$\" -osint -url $\"%1$\""
 
   ; Associate the file handlers with FirefoxHTML, if they aren't already.
   ReadRegStr $6 SHCTX "$0\.htm" ""
   ${WordFind} "$6" "-" "+1{" $6
   ${If} "$6" != "FirefoxHTML"
-    WriteRegStr SHCTX "$0\.htm"   "" "FirefoxHTML-$AppUserModelID"
+    WriteRegStr SHCTX "$0\.htm"   "" "FirefoxHTML$5"
   ${EndIf}
 
   ReadRegStr $6 SHCTX "$0\.html" ""
   ${WordFind} "$6" "-" "+1{" $6
   ${If} "$6" != "FirefoxHTML"
-    WriteRegStr SHCTX "$0\.html"  "" "FirefoxHTML-$AppUserModelID"
+    WriteRegStr SHCTX "$0\.html"  "" "FirefoxHTML$5"
   ${EndIf}
 
   ReadRegStr $6 SHCTX "$0\.shtml" ""
   ${WordFind} "$6" "-" "+1{" $6
   ${If} "$6" != "FirefoxHTML"
-    WriteRegStr SHCTX "$0\.shtml" "" "FirefoxHTML-$AppUserModelID"
+    WriteRegStr SHCTX "$0\.shtml" "" "FirefoxHTML$5"
   ${EndIf}
 
   ReadRegStr $6 SHCTX "$0\.xht" ""
   ${WordFind} "$6" "-" "+1{" $6
   ${If} "$6" != "FirefoxHTML"
-    WriteRegStr SHCTX "$0\.xht"   "" "FirefoxHTML-$AppUserModelID"
+    WriteRegStr SHCTX "$0\.xht"   "" "FirefoxHTML$5"
   ${EndIf}
 
   ReadRegStr $6 SHCTX "$0\.xhtml" ""
   ${WordFind} "$6" "-" "+1{" $6
   ${If} "$6" != "FirefoxHTML"
-    WriteRegStr SHCTX "$0\.xhtml" "" "FirefoxHTML-$AppUserModelID"
+    WriteRegStr SHCTX "$0\.xhtml" "" "FirefoxHTML$5"
   ${EndIf}
 
-  ${AddAssociationIfNoneExist} ".pdf"
-  ${AddAssociationIfNoneExist} ".oga"
-  ${AddAssociationIfNoneExist} ".ogg"
-  ${AddAssociationIfNoneExist} ".ogv"
-  ${AddAssociationIfNoneExist} ".pdf"
-  ${AddAssociationIfNoneExist} ".webm"
+  ${AddAssociationIfNoneExist} ".pdf" "FirefoxHTML$5"
+  ${AddAssociationIfNoneExist} ".oga" "FirefoxHTML$5"
+  ${AddAssociationIfNoneExist} ".ogg" "FirefoxHTML$5"
+  ${AddAssociationIfNoneExist} ".ogv" "FirefoxHTML$5"
+  ${AddAssociationIfNoneExist} ".pdf" "FirefoxHTML$5"
+  ${AddAssociationIfNoneExist} ".webm" "FirefoxHTML$5"
 
   ; An empty string is used for the 5th param because FirefoxHTML is not a
   ; protocol handler
-  ${AddDisabledDDEHandlerValues} "FirefoxHTML-$AppUserModelID" "$2" "$8,1" \
+  ${AddDisabledDDEHandlerValues} "FirefoxHTML$5" "$2" "$8,1" \
                                  "${AppRegName} HTML Document" ""
 
-  ${AddDisabledDDEHandlerValues} "FirefoxURL-$AppUserModelID" "$2" "$8,1" "${AppRegName} URL" \
+  ${AddDisabledDDEHandlerValues} "FirefoxURL$5" "$2" "$8,1" "${AppRegName} URL" \
                                  "true"
   ; An empty string is used for the 4th & 5th params because the following
   ; protocol handlers already have a display name and the additional keys
   ; required for a protocol handler.
   ${AddDisabledDDEHandlerValues} "ftp" "$2" "$8,1" "" ""
   ${AddDisabledDDEHandlerValues} "http" "$2" "$8,1" "" ""
   ${AddDisabledDDEHandlerValues} "https" "$2" "$8,1" "" ""
 !macroend
@@ -381,82 +399,87 @@
 ;
 ; This function also writes our RegisteredApplications entry, which gets us
 ; listed in the Settings app's default browser options on Windows 8+, and in
 ; Set Program Access and Defaults on earlier versions.
 !macro SetStartMenuInternet RegKey
   ${GetLongPath} "$INSTDIR\${FileMainEXE}" $8
   ${GetLongPath} "$INSTDIR\uninstall\helper.exe" $7
 
-  StrCpy $0 "Software\Clients\StartMenuInternet\${AppRegName}-$AppUserModelID"
-
-  WriteRegStr ${RegKey} "$0" "" "${BrandFullName}"
-
-  WriteRegStr ${RegKey} "$0\DefaultIcon" "" "$8,0"
+  ; Avoid writing new keys at the hash-suffixed path if this installation
+  ; already has keys at the old FIREFOX.EXE path. Otherwise we would create a
+  ; second entry in Default Apps for the same installation.
+  ${StrFilter} "${FileMainEXE}" "+" "" "" $1
+  ReadRegStr $0 ${RegKey} "Software\Clients\StartMenuInternet\$1\DefaultIcon" ""
+  StrCpy $0 $0 -2
+  ${If} $0 != $8
+    StrCpy $0 "Software\Clients\StartMenuInternet\${AppRegName}-$AppUserModelID"
 
-  ; The Reinstall Command is defined at
-  ; http://msdn.microsoft.com/library/default.asp?url=/library/en-us/shellcc/platform/shell/programmersguide/shell_adv/registeringapps.asp
-  WriteRegStr ${RegKey} "$0\InstallInfo" "HideIconsCommand" "$\"$7$\" /HideShortcuts"
-  WriteRegStr ${RegKey} "$0\InstallInfo" "ShowIconsCommand" "$\"$7$\" /ShowShortcuts"
-  WriteRegStr ${RegKey} "$0\InstallInfo" "ReinstallCommand" "$\"$7$\" /SetAsDefaultAppGlobal"
+    WriteRegStr ${RegKey} "$0" "" "${BrandFullName}"
 
-  ClearErrors
-  ReadRegDWORD $1 ${RegKey} "$0\InstallInfo" "IconsVisible"
-  ; If the IconsVisible name value pair doesn't exist add it otherwise the
-  ; application won't be displayed in Set Program Access and Defaults.
-  ${If} ${Errors}
-    ${If} ${FileExists} "$QUICKLAUNCH\${BrandFullName}.lnk"
-      WriteRegDWORD ${RegKey} "$0\InstallInfo" "IconsVisible" 1
-    ${Else}
-      WriteRegDWORD ${RegKey} "$0\InstallInfo" "IconsVisible" 0
-    ${EndIf}
-  ${EndIf}
+    WriteRegStr ${RegKey} "$0\DefaultIcon" "" "$8,0"
 
-  WriteRegStr ${RegKey} "$0\shell\open\command" "" "$\"$8$\""
+    ; The Reinstall Command is defined at
+    ; http://msdn.microsoft.com/library/default.asp?url=/library/en-us/shellcc/platform/shell/programmersguide/shell_adv/registeringapps.asp
+    WriteRegStr ${RegKey} "$0\InstallInfo" "HideIconsCommand" "$\"$7$\" /HideShortcuts"
+    WriteRegStr ${RegKey} "$0\InstallInfo" "ShowIconsCommand" "$\"$7$\" /ShowShortcuts"
+    WriteRegStr ${RegKey} "$0\InstallInfo" "ReinstallCommand" "$\"$7$\" /SetAsDefaultAppGlobal"
+    WriteRegDWORD ${RegKey} "$0\InstallInfo" "IconsVisible" 1
+
+    WriteRegStr ${RegKey} "$0\shell\open\command" "" "$\"$8$\""
 
-  WriteRegStr ${RegKey} "$0\shell\properties" "" "$(CONTEXT_OPTIONS)"
-  WriteRegStr ${RegKey} "$0\shell\properties\command" "" "$\"$8$\" -preferences"
+    WriteRegStr ${RegKey} "$0\shell\properties" "" "$(CONTEXT_OPTIONS)"
+    WriteRegStr ${RegKey} "$0\shell\properties\command" "" "$\"$8$\" -preferences"
 
-  WriteRegStr ${RegKey} "$0\shell\safemode" "" "$(CONTEXT_SAFE_MODE)"
-  WriteRegStr ${RegKey} "$0\shell\safemode\command" "" "$\"$8$\" -safe-mode"
+    WriteRegStr ${RegKey} "$0\shell\safemode" "" "$(CONTEXT_SAFE_MODE)"
+    WriteRegStr ${RegKey} "$0\shell\safemode\command" "" "$\"$8$\" -safe-mode"
 
-  ; Capabilities registry keys
-  WriteRegStr ${RegKey} "$0\Capabilities" "ApplicationDescription" "$(REG_APP_DESC)"
-  WriteRegStr ${RegKey} "$0\Capabilities" "ApplicationIcon" "$8,0"
-  WriteRegStr ${RegKey} "$0\Capabilities" "ApplicationName" "${BrandShortName}"
+    ; Capabilities registry keys
+    WriteRegStr ${RegKey} "$0\Capabilities" "ApplicationDescription" "$(REG_APP_DESC)"
+    WriteRegStr ${RegKey} "$0\Capabilities" "ApplicationIcon" "$8,0"
+    WriteRegStr ${RegKey} "$0\Capabilities" "ApplicationName" "${BrandShortName}"
 
-  WriteRegStr ${RegKey} "$0\Capabilities\FileAssociations" ".htm"   "FirefoxHTML-$AppUserModelID"
-  WriteRegStr ${RegKey} "$0\Capabilities\FileAssociations" ".html"  "FirefoxHTML-$AppUserModelID"
-  WriteRegStr ${RegKey} "$0\Capabilities\FileAssociations" ".shtml" "FirefoxHTML-$AppUserModelID"
-  WriteRegStr ${RegKey} "$0\Capabilities\FileAssociations" ".xht"   "FirefoxHTML-$AppUserModelID"
-  WriteRegStr ${RegKey} "$0\Capabilities\FileAssociations" ".xhtml" "FirefoxHTML-$AppUserModelID"
+    WriteRegStr ${RegKey} "$0\Capabilities\FileAssociations" ".htm"   "FirefoxHTML-$AppUserModelID"
+    WriteRegStr ${RegKey} "$0\Capabilities\FileAssociations" ".html"  "FirefoxHTML-$AppUserModelID"
+    WriteRegStr ${RegKey} "$0\Capabilities\FileAssociations" ".shtml" "FirefoxHTML-$AppUserModelID"
+    WriteRegStr ${RegKey} "$0\Capabilities\FileAssociations" ".xht"   "FirefoxHTML-$AppUserModelID"
+    WriteRegStr ${RegKey} "$0\Capabilities\FileAssociations" ".xhtml" "FirefoxHTML-$AppUserModelID"
+
+    WriteRegStr ${RegKey} "$0\Capabilities\StartMenu" "StartMenuInternet" "${AppRegName}-$AppUserModelID"
 
-  WriteRegStr ${RegKey} "$0\Capabilities\StartMenu" "StartMenuInternet" "${AppRegName}-$AppUserModelID"
+    WriteRegStr ${RegKey} "$0\Capabilities\URLAssociations" "ftp"    "FirefoxURL-$AppUserModelID"
+    WriteRegStr ${RegKey} "$0\Capabilities\URLAssociations" "http"   "FirefoxURL-$AppUserModelID"
+    WriteRegStr ${RegKey} "$0\Capabilities\URLAssociations" "https"  "FirefoxURL-$AppUserModelID"
 
-  WriteRegStr ${RegKey} "$0\Capabilities\URLAssociations" "ftp"    "FirefoxURL-$AppUserModelID"
-  WriteRegStr ${RegKey} "$0\Capabilities\URLAssociations" "http"   "FirefoxURL-$AppUserModelID"
-  WriteRegStr ${RegKey} "$0\Capabilities\URLAssociations" "https"  "FirefoxURL-$AppUserModelID"
-
-  ; Registered Application
-  WriteRegStr ${RegKey} "Software\RegisteredApplications" "${AppRegName}-$AppUserModelID" "$0\Capabilities"
+    ; Registered Application
+    WriteRegStr ${RegKey} "Software\RegisteredApplications" "${AppRegName}-$AppUserModelID" "$0\Capabilities"
+  ${EndIf}
 !macroend
 !define SetStartMenuInternet "!insertmacro SetStartMenuInternet"
 
 ; The IconHandler reference for FirefoxHTML can end up in an inconsistent state
 ; due to changes not being detected by the IconHandler for side by side
 ; installs (see bug 268512). The symptoms can be either an incorrect icon or no
 ; icon being displayed for files associated with Firefox (does not use SHCTX).
 !macro FixShellIconHandler RegKey
+  ; Find the correct key to update, either FirefoxHTML or FirefoxHTML-[PathHash]
+  StrCpy $3 "FirefoxHTML-$AppUserModelID"
   ClearErrors
-  ReadRegStr $1 ${RegKey} "Software\Classes\FirefoxHTML-$AppUserModelID\ShellEx\IconHandler" ""
+  ReadRegStr $0 ${RegKey} "Software\Classes\$3\DefaultIcon" ""
+  ${If} ${Errors}
+    StrCpy $3 "FirefoxHTML"
+  ${EndIf}
+
+  ClearErrors
+  ReadRegStr $1 ${RegKey} "Software\Classes\$3\ShellEx\IconHandler" ""
   ${Unless} ${Errors}
-    ReadRegStr $1 ${RegKey} "Software\Classes\FirefoxHTML-$AppUserModelID\DefaultIcon" ""
+    ReadRegStr $1 ${RegKey} "Software\Classes\$3\DefaultIcon" ""
     ${GetLongPath} "$INSTDIR\${FileMainEXE}" $2
     ${If} "$1" != "$2,1"
-      WriteRegStr ${RegKey} "Software\Classes\FirefoxHTML-$AppUserModelID\DefaultIcon" "" "$2,1"
+      WriteRegStr ${RegKey} "Software\Classes\$3\DefaultIcon" "" "$2,1"
     ${EndIf}
   ${EndUnless}
 !macroend
 !define FixShellIconHandler "!insertmacro FixShellIconHandler"
 
 ; Add Software\Mozilla\ registry entries (uses SHCTX).
 !macro SetAppKeys
   ; Check if this is an ESR release and if so add registry values so it is
@@ -601,17 +624,17 @@
     ; value from both HKCU and HKLM if it set to FirefoxHTML.
     ${If} "$0" == "FirefoxHTML"
       DeleteRegValue HKCU "Software\Classes\${FILE_TYPE}" ""
     ${EndIf}
     ${If} "$1" == "FirefoxHTML"
       DeleteRegValue HKLM "Software\Classes\${FILE_TYPE}" ""
     ${EndIf}
   ${ElseIf} "$0" == "FirefoxHTML"
-    ; Since KHCU is set to FirefoxHTML remove FirefoxHTML as the default value
+    ; Since HKCU is set to FirefoxHTML remove FirefoxHTML as the default value
     ; from HKCU if HKLM is set to a value other than an empty string.
     ${If} "$1" != ""
       DeleteRegValue HKCU "Software\Classes\${FILE_TYPE}" ""
     ${EndIf}
   ${EndIf}
 !macroend
 !define FixBadFileAssociation "!insertmacro FixBadFileAssociation"
 
@@ -663,22 +686,34 @@
   ; for this install location.
 
   ${IsHandlerForInstallDir} "FirefoxHTML-$AppUserModelID" $R9
   ${If} "$R9" == "true"
     ; An empty string is used for the 5th param because FirefoxHTML is not a
     ; protocol handler.
     ${AddDisabledDDEHandlerValues} "FirefoxHTML-$AppUserModelID" "$2" "$8,1" \
                                    "${AppRegName} HTML Document" ""
+  ${Else}
+    ${IsHandlerForInstallDir} "FirefoxHTML" $R9
+    ${If} "$R9" == "true"
+      ${AddDisabledDDEHandlerValues} "FirefoxHTML" "$2" "$8,1" \
+                                     "${AppRegName} HTML Document" ""
+    ${EndIf}
   ${EndIf}
 
   ${IsHandlerForInstallDir} "FirefoxURL-$AppUserModelID" $R9
   ${If} "$R9" == "true"
     ${AddDisabledDDEHandlerValues} "FirefoxURL-$AppUserModelID" "$2" "$8,1" \
                                    "${AppRegName} URL" "true"
+  ${Else}
+    ${IsHandlerForInstallDir} "FirefoxURL" $R9
+    ${If} "$R9" == "true"
+      ${AddDisabledDDEHandlerValues} "FirefoxURL" "$2" "$8,1" \
+                                     "${AppRegName} URL" "true"
+    ${EndIf}
   ${EndIf}
 
   ; An empty string is used for the 4th & 5th params because the following
   ; protocol handlers already have a display name and the additional keys
   ; required for a protocol handler.
   ${IsHandlerForInstallDir} "ftp" $R9
   ${If} "$R9" == "true"
     ${AddDisabledDDEHandlerValues} "ftp" "$2" "$8,1" "" ""
@@ -1210,33 +1245,45 @@
 ; Sets this installation as the default browser by setting the registry keys
 ; under HKEY_CURRENT_USER via registry calls and using the AppAssocReg NSIS
 ; plugin. This is a function instead of a macro so it is
 ; easily called from an elevated instance of the binary. Since this can be
 ; called by an elevated instance logging is not performed in this function.
 Function SetAsDefaultAppUserHKCU
   ; Only set as the user's StartMenuInternet browser if the StartMenuInternet
   ; registry keys are for this install.
-  ${StrFilter} "${FileMainEXE}" "+" "" "" $R9
+  StrCpy $R9 "${AppRegName}-$AppUserModelID"
   ClearErrors
-  ReadRegStr $0 HKCU "Software\Clients\StartMenuInternet\$R9-$AppUserModelID\DefaultIcon" ""
+  ReadRegStr $0 HKCU "Software\Clients\StartMenuInternet\$R9\DefaultIcon" ""
   ${If} ${Errors}
   ${OrIf} ${AtMostWin2008R2}
     ClearErrors
-    ReadRegStr $0 HKLM "Software\Clients\StartMenuInternet\$R9-$AppUserModelID\DefaultIcon" ""
+    ReadRegStr $0 HKLM "Software\Clients\StartMenuInternet\$R9\DefaultIcon" ""
   ${EndIf}
   ${Unless} ${Errors}
-    ${GetPathFromString} "$0" $0
-    ${GetParent} "$0" $0
-    ${If} ${FileExists} "$0"
-      ${GetLongPath} "$0" $0
-      ${If} "$0" == "$INSTDIR"
-        WriteRegStr HKCU "Software\Clients\StartMenuInternet" "" "$R9-$AppUserModelID"
+    WriteRegStr HKCU "Software\Clients\StartMenuInternet" "" "$R9"
+  ${Else}
+    ${StrFilter} "${FileMainEXE}" "+" "" "" $R9
+    ClearErrors
+    ReadRegStr $0 HKCU "Software\Clients\StartMenuInternet\$R9\DefaultIcon" ""
+    ${If} ${Errors}
+    ${OrIf} ${AtMostWin2008R2}
+      ClearErrors
+      ReadRegStr $0 HKLM "Software\Clients\StartMenuInternet\$R9\DefaultIcon" ""
+    ${EndIf}
+    ${Unless} ${Errors}
+      ${GetPathFromString} "$0" $0
+      ${GetParent} "$0" $0
+      ${If} ${FileExists} "$0"
+        ${GetLongPath} "$0" $0
+        ${If} "$0" == "$INSTDIR"
+          WriteRegStr HKCU "Software\Clients\StartMenuInternet" "" "$R9"
+        ${EndIf}
       ${EndIf}
-    ${EndIf}
+    ${EndUnless}
   ${EndUnless}
 
   SetShellVarContext current  ; Set SHCTX to the current user (e.g. HKCU)
 
   ${If} ${AtLeastWin8}
     ${SetStartMenuInternet} "HKCU"
     ${FixShellIconHandler} "HKCU"
     ${FixClassKeys} ; Does not use SHCTX
@@ -1244,21 +1291,21 @@ Function SetAsDefaultAppUserHKCU
 
   ${SetHandlers}
 
   ; Only register as the handler if the app registry name
   ; exists under the RegisteredApplications registry key. The protocol and
   ; file handlers set previously at the user level will associate this install
   ; as the default browser.
   ClearErrors
-  ReadRegStr $0 HKLM "Software\RegisteredApplications" "${AppRegName}-$AppUserModelID"
+  ReadRegStr $0 HKLM "Software\RegisteredApplications" "$R9"
   ${Unless} ${Errors}
     ; This is all protected by a user choice hash in Windows 8 so it won't
     ; help, but it also won't hurt.
-    AppAssocReg::SetAppAsDefaultAll "${AppRegName}-$AppUserModelID"
+    AppAssocReg::SetAppAsDefaultAll "$R9"
   ${EndUnless}
   ${RemoveDeprecatedKeys}
   ${MigrateTaskBarShortcut}
 FunctionEnd
 
 ; Helper for updating the shortcut application model IDs.
 Function FixShortcutAppModelIDs
   ${If} ${AtLeastWin7}
@@ -1300,24 +1347,34 @@ Function SetAsDefaultAppUser
     Return ; Nothing more needs to be done
   ${EndIf}
 
   ; Before Win8, it is only possible to set this installation of the application
   ; as the StartMenuInternet handler if it was added to the HKLM
   ; StartMenuInternet registry keys.
   ; http://support.microsoft.com/kb/297878
 
-  ; Check if this install location registered as the StartMenuInternet client
+  ; Check if this install location registered as a StartMenuInternet client
   ClearErrors
   ReadRegStr $0 HKCU "Software\Clients\StartMenuInternet\${AppRegName}-$AppUserModelID\DefaultIcon" ""
   ${If} ${Errors}
   ${OrIf} ${AtMostWin2008R2}
     ClearErrors
     ReadRegStr $0 HKLM "Software\Clients\StartMenuInternet\${AppRegName}-$AppUserModelID\DefaultIcon" ""
   ${EndIf}
+  ${If} ${Errors}
+    ${StrFilter} "${FileMainEXE}" "+" "" "" $R9
+    ClearErrors
+    ReadRegStr $0 HKCU "Software\Clients\StartMenuInternet\$R9\DefaultIcon" ""
+  ${EndIf}
+  ${If} ${Errors}
+  ${OrIf} ${AtMostWin2008R2}
+    ClearErrors
+    ReadRegStr $0 HKLM "Software\Clients\StartMenuInternet\$R9\DefaultIcon" ""
+  ${EndIf}
 
   ${Unless} ${Errors}
     ${GetPathFromString} "$0" $0
     ${GetParent} "$0" $0
     ${If} ${FileExists} "$0"
       ${GetLongPath} "$0" $0
       ${If} "$0" == "$INSTDIR"
         ; Check if this is running in an elevated process