diff --git a/development/Win32/packaging/AltInstaller/InstallActions-update.nsh b/development/Win32/packaging/AltInstaller/InstallActions-update.nsh
index 0dcfdbb245..c5e0cfc416 100644
--- a/development/Win32/packaging/AltInstaller/InstallActions-update.nsh
+++ b/development/Win32/packaging/AltInstaller/InstallActions-update.nsh
@@ -127,6 +127,17 @@ Section "-Installation actions" SecInstallation
   ExecWait '"$INSTDIR\Resources\configLyX.bat"'
   Delete "$INSTDIR\Resources\configLyX.bat"
   
+  # there might be the case that python files need to be updated
+  # but this should only be done when Python is not installed
+  ReadRegStr $PythonPath HKLM "Software\Python\PythonCore\2.5\InstallPath" ""
+  ${if} $PythonPath == ""
+   ReadRegStr $PythonPath HKLM "Software\Python\PythonCore\2.6\InstallPath" ""
+  ${endif}
+  ${if} $PythonPath != ""
+   RMDir /r $INSTDIR\bin\Lib
+   RMDir /r $INSTDIR\bin\DLLs
+  ${endif}
+  
   # for some unknown odd reason the folder $INSTDIR_OLD\Resources\ui
   # is not deleted in function InstDirChange, so the deletion has to be called
   # again to make it work
@@ -165,9 +176,6 @@ Function InstDirChange
    StrCpy $NewString "LyX ${PRODUCT_VERSION}"
    # following macro from TextFunc.nsh # calls Function ReplaceLineContent from LyXUtils.nsh
    ${LineFind} "$INSTDIR\Resources\lyxrc.dist" "" "1:-1" "ReplaceLineContent"
-   # this is only needed for this installer version 4.18 (delete it afterwards!)
-    StrCpy $OldString "LyX 1.6.0"
-    ${LineFind} "$INSTDIR\Resources\lyxrc.dist" "" "1:-1" "ReplaceLineContent"
    
    # set the new path to the preferences file for all users
    StrCpy $FileName "preferences"
@@ -203,8 +211,6 @@ Function RefreshRegUninst
   # Aspell
   ReadRegStr $0 SHCTX "Software\Aspell" "OnlyWithLyX" # special entry to test if it was installed with LyX
   ${if} $0 == "Yes${PRODUCT_VERSION_SHORT_OLD}"
-  # this is only needed for this installer version 4.18 (delete it afterwards!)
-   ${orif} $0 == "Yes160"
    WriteRegStr HKLM "SOFTWARE\Aspell" "OnlyWithLyX" "Yes${PRODUCT_VERSION_SHORT}"
   ${endif}
   
@@ -213,8 +219,6 @@ Function RefreshRegUninst
   StrCpy $RegLocation "SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Metafile to EPS Converter"
   ReadRegStr $0 SHCTX "$RegLocation" "OnlyWithLyX"
   ${if} $0 == "Yes${PRODUCT_VERSION_SHORT_OLD}"
-  # this is only needed for this installer version 4.18 (delete it afterwards!)
-  ${orif} $0 == "Yes160"
    WriteRegStr HKLM "$RegLocation" "OnlyWithLyX" "Yes${PRODUCT_VERSION_SHORT}"
    # set the new path
    ReadRegStr $0 HKLM "SOFTWARE\InkNote Selector" ""
@@ -223,28 +227,17 @@ Function RefreshRegUninst
    ReadRegStr $0 HKLM "$RegLocation" "InstallLocation"
    ${WordReplace} $0 "${PRODUCT_VERSION_OLD}" "LyX ${PRODUCT_VERSION}" "+" $0
    WriteRegStr HKLM "$RegLocation" "InstallLocation" "$0"
-   # this is only needed for this installer version 4.18 (delete it afterwards!)
-    ReadRegStr $0 HKLM "SOFTWARE\InkNote Selector" ""
-    ${WordReplace} $0 "LyX 1.6.0" "LyX ${PRODUCT_VERSION}" "+" $0
-    WriteRegStr HKLM "SOFTWARE\InkNote Selector" "" "$0"
-    ReadRegStr $0 HKLM "$RegLocation" "InstallLocation"
-    ${WordReplace} $0 "LyX 1.6.0" "LyX ${PRODUCT_VERSION}" "+" $0
-    WriteRegStr HKLM "$RegLocation" "InstallLocation" "$0"
   ${endif}
   
   # MiKTeX
   ReadRegStr $0 HKLM "SOFTWARE\MiKTeX.org\MiKTeX" "OnlyWithLyX"
   ${if} $0 == "Yes${PRODUCT_VERSION_SHORT_OLD}"
-  # this is only needed for this installer version 4.18 (delete it afterwards!)
-  ${orif} $0 == "Yes160"
    WriteRegStr HKLM "SOFTWARE\MiKTeX.org\MiKTeX" "OnlyWithLyX" "Yes${PRODUCT_VERSION_SHORT}"
   ${endif}
   
   # JabRef
   ReadRegStr $0 HKLM "Software\Microsoft\Windows\CurrentVersion\Uninstall\JabRef ${JabRefVersion}" "OnlyWithLyX"
   ${if} $0 == "Yes${PRODUCT_VERSION_SHORT_OLD}"
-  # this is only needed for this installer version 4.18 (delete it afterwards!)
-  ${orif} $0 == "Yes160"
    WriteRegStr HKLM "SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\JabRef ${JabRefVersion}" "OnlyWithLyX" "Yes${PRODUCT_VERSION_SHORT}"
   ${endif}