diff --git a/admin/win/msi/CMakeLists.txt b/admin/win/msi/CMakeLists.txt
index 933037dac115..90f7af9d0c85 100644
--- a/admin/win/msi/CMakeLists.txt
+++ b/admin/win/msi/CMakeLists.txt
@@ -29,6 +29,8 @@ install(FILES
         Nextcloud.wxs
         ${CMAKE_CURRENT_BINARY_DIR}/RegistryCleanup.vbs
         RegistryCleanupCustomAction.wxs
+        UinstallOldClientDlg.wxs
+        License.rtf
         gui/banner.bmp
         gui/dialog.bmp
     DESTINATION msi/)
diff --git a/admin/win/msi/License.rtf b/admin/win/msi/License.rtf
new file mode 100644
index 000000000000..c5550a6c51b0
Binary files /dev/null and b/admin/win/msi/License.rtf differ
diff --git a/admin/win/msi/Nextcloud.wxs b/admin/win/msi/Nextcloud.wxs
index 4719d85dc0ac..98dc0e29db73 100644
--- a/admin/win/msi/Nextcloud.wxs
+++ b/admin/win/msi/Nextcloud.wxs
@@ -45,7 +45,6 @@
         https://www.joyofsetup.com/2010/01/16/major-upgrades-now-easier-than-ever/
     -->
     <MajorUpgrade Schedule="afterInstallInitialize" AllowDowngrades="yes" />
-    <Property Id="REINSTALLMODE" Value="amus" />
 
     <Media Id="1" Cabinet="$(var.AppShortName).cab" EmbedCab="yes" />
 
@@ -54,6 +53,8 @@
         <RegistrySearch Id="RegistryInstallDir" Type="raw" Root="HKLM" Key="Software\$(var.AppVendor)\$(var.AppName)" Win64="no" />
     </Property>
 
+    <Property Id="OLDCLIENTDIR">C:\Windows\System32\</Property>
+
     <!-- Detect legacy NSIS installation -->
     <Property Id="NSIS_UNINSTALLEXE">
         <RegistrySearch Id="RegistryLegacyUninstallString" Type="file" Root="HKLM" Key="Software\Microsoft\Windows\CurrentVersion\Uninstall\$(var.AppName)" Name="UninstallString" Win64="no">
@@ -65,6 +66,11 @@
         <RegistrySearch Id="RegIsPrevVersionShellExtCloseSupported" Type="raw" Root="HKLM" Key="Software\$(var.AppVendor)\$(var.AppName)" Name="isShellExtCloseSupported" Win64="$(var.PlatformWin64)" />
     </Property>
 
+   <!-- <Property Id="UNINSTALL_OLD">
+        <RegistrySearch Id="RegistryLegacyUninstallString" Type="file" Root="HKLM" Key="Software\Microsoft\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall\$("MagentaCLOUD Software")" Name="UninstallString" Win64="no">
+            </RegistrySearch>
+    </Property>-->
+
     <!-- Property to disable update checks -->
     <Property Id="SKIPAUTOUPDATE" Value="0" />
 
@@ -80,6 +86,59 @@
     <SetProperty Id="ExecNsisUninstaller" Value="&quot;$(var.AppShortName)&quot; &quot;[NSIS_UNINSTALLEXE]&quot;" Before="ExecNsisUninstaller" Sequence="execute" />
     <SetProperty Id="RemoveNavigationPaneEntries" Value="&quot;$(var.AppName)&quot;" Before="RemoveNavigationPaneEntries" Sequence="execute" />
 
+    <!-- Detect the old client by its upgrade id -->
+   <!-- <Upgrade Id="21BAADEB-079C-4503-B99A-D49A34D8C525">
+        <UpgradeVersion OnlyDetect='no' Property='OLDFOUND' 
+            Minimum="0.0.0.0" IncludeMinimum="yes"
+            Maximum='99.0.0.0' IncludeMaximum='yes' />
+    </Upgrade> -->
+    <CustomAction Id="UninstallOldClient"
+        Script="vbscript"
+        Execute="immediate">
+        <![CDATA[
+                const HKEY_CLASSES_ROOT   = &H80000000
+                const HKEY_CURRENT_USER   = &H80000001
+                const HKEY_LOCAL_MACHINE  = &H80000002
+                const HKEY_USERS          = &H80000003
+                const HKEY_CURRENT_CONFIG = &H80000004
+                const HKEY_DYN_DATA       = &H80000005
+                strComputer = "."
+                oldClientExists = False
+                userName = CreateObject("WScript.Network").UserName
+                configPath = "C:\Users\"& userName &"\AppData\Roaming\MagentaCLOUD"
+                configFile = configPath & "\magentacloud.cfg"
+                jsonPath = "C:\Users\"& userName &"\AppData\Local\MagentaCLOUD"
+                jsonFile = jsonFile & "\magentacloud.cfg"
+
+                set oWsh = createobject("wscript.shell")
+                Set oReg = GetObject("winmgmts:{impersonationLevel=impersonate}!\\" _
+                         & strComputer & "\root\default:StdRegProv")
+
+                strKeyPath = "software\WOW6432Node\microsoft\windows\currentversion\uninstall" ' Root level
+                oReg.EnumKey HKEY_LOCAL_MACHINE, strKeyPath, arrSubKeys
+
+                For Each subkey In arrSubKeys
+                  on error resume next
+                  sDisplayName = oWsh.Regread("HKLM\" & strKeyPath & "\" & subkey & "\DisplayName")
+                  if err.number = 0 then
+                    on error goto 0
+                    if sDisplayName = "MagentaCLOUD Software" then
+                        oldClientExists = True
+                        sUninstall = oWsh.Regread("HKLM\" & strKeyPath & "\" & subkey & "\UnInstallString")
+                    End If
+                  End If
+                Next
+                on error goto 0
+
+                if oldClientExists Then
+                    sUninstall = sUnInstall & " /qn"
+                    command = "/k " & sUninstall
+                    Set objShell = CreateObject("Shell.Application")
+                    objShell.ShellExecute "cmd.exe", command, "", "runas", 0
+
+                End If
+        ]]>
+    </CustomAction>
     <InstallExecuteSequence>
       <Custom Action="SetCfApiWindowClassName" Before="InstallValidate"/>
       <Custom Action="CloseCfApiShellExtension" After="SetCfApiWindowClassName" />
@@ -128,18 +187,27 @@
     -->
 
     <!-- Custom license -->
-    <!--
     <WixVariable Id="WixUILicenseRtf" Value="$(var.AppLicenseRtf)" />
-    -->
 
     <UI>
         <UIRef Id="WixUI_FeatureTree" />
         <UIRef Id="WixUI_ErrorProgressText" />
 
-        <!-- Skip the license page -->
-        <Publish Dialog="WelcomeDlg" Control="Next" Event="NewDialog" Value="CustomizeDlg" Order="3">1</Publish>
-        <!-- Skip the page on the way back too -->
-        <Publish Dialog="CustomizeDlg" Control="Back" Event="NewDialog" Value="WelcomeDlg" Order="3">1</Publish>
+        <Publish Dialog="WelcomeDlg" Control="Next" Event="NewDialog" Value="LicenseAgreementDlg" Order="3">1</Publish>
+        <Publish Dialog="LicenseAgreementDlg" Control="Next" Event="NewDialog" Value="CustomizeDlg" Order="3">1</Publish>
+        <Publish Dialog="CustomizeDlg" Control="Back" Event="NewDialog" Value="LicenseAgreementDlg" Order="3">1</Publish>
+
+     <!--   <Publish Dialog="MigrationDialog"
+            Control="Finish"
+            Event="DoAction"
+            Value="RemoveOldClient">NOT Installed</Publish> -->
+
+     <!--   <Publish Dialog="MigrationDialog" Control="cancelButton" Event="EndDialog" Value="ExitDialog">1</Publish> -->
+        <UIRef Id="MigrationDialogUI"/>
+
+        <Publish Dialog="MigrationDialog" Control="Weiter"
+            Event="DoAction" Value="UninstallOldClient">Not Installed</Publish>
+       <Publish Dialog="MigrationDialog" Control="Weiter" Event="EndDialog" Value="Return">1</Publish>
 
         <!-- https://wixtoolset.org/documentation/manual/v3/howtos/ui_and_localization/run_program_after_install.html -->        
         <Publish Dialog="ExitDialog" 
@@ -155,15 +223,17 @@
     <!-- "Launch" checkbox -->
     <Property Id="WixShellExecTarget" Value="[#MainExecutable]" />
     <CustomAction Id="LaunchApplication" BinaryKey="WixCA" DllEntry="WixShellExec" Impersonate="yes" />
-    <Property Id="WIXUI_EXITDIALOGOPTIONALCHECKBOXTEXT" Value="Launch $(var.AppName)" />
+    <Property Id="WIXUI_EXITDIALOGOPTIONALCHECKBOXTEXT" Value="$(var.AppName) starten" />
     <SetProperty Id="WIXUI_EXITDIALOGOPTIONALCHECKBOX" Value="1" Before="CostInitialize">NOT (LAUNCH=0)</SetProperty>
 
     <!-- Components -->
     <Directory Id="TARGETDIR" Name="SourceDir">
         <Directory Id="$(var.PlatformProgramFilesFolder)" Name="PFiles">
             <Directory Id="INSTALLDIR" Name="$(var.AppName)">
+                <Directory Id="OLDCLIENTDIR" Name="UninstallString">
                 <!-- Shell Extensions -->
-                <Directory Id="ShellExtDir" />
+                    <Directory Id="ShellExtDir" Name="shellext" />
+                </Directory>
             </Directory>
         </Directory>
 
diff --git a/admin/win/msi/OEM.wxi.in b/admin/win/msi/OEM.wxi.in
index ae8f964e28f5..dbc847a5c762 100644
--- a/admin/win/msi/OEM.wxi.in
+++ b/admin/win/msi/OEM.wxi.in
@@ -22,6 +22,7 @@
     <!-- App Defines -->
     <?define AppName = "@APPLICATION_NAME@" ?>
     <?define AppShortName = "@APPLICATION_EXECUTABLE@" ?>
+    <?define OldAppName = "MagentaCLOUD Software" ?>
 
     <?define AppIcon = "@APPLICATION_ICON_NAME@.ico" ?>
     <?define AppExe = "@APPLICATION_EXECUTABLE@.exe" ?>
@@ -36,9 +37,8 @@
     <?define NCContextMenuShellextWndClassName = "@NCCONTEXTMENU_SHELLEXT_WINDOW_CLASS_NAME@" ?>
 
     <!-- Custom license: To use it, also remove the "Skip the license page" stuff in the <UI> section
-                         and uncomment <WixVariable Id="WixUILicenseRtf"...
-    <?define AppLicenseRtf = "path\License.rtf" ?>
-    -->
+                         and uncomment <WixVariable Id="WixUILicenseRtf"...-->
+    <?define AppLicenseRtf = "$(sys.CURRENTDIR)\License.rtf" ?>
 
     <!-- App Version -->
     <?define VerMajor = "@MIRALL_VERSION_MAJOR@" ?>
diff --git a/admin/win/msi/RegistryCleanup.vbs b/admin/win/msi/RegistryCleanup.vbs
new file mode 100644
index 000000000000..50e26c8ca7ed
--- /dev/null
+++ b/admin/win/msi/RegistryCleanup.vbs
@@ -0,0 +1,54 @@
+On Error goto 0
+
+Const HKEY_LOCAL_MACHINE = &H80000002
+
+Const strObjRegistry = "winmgmts:\\.\root\default:StdRegProv"
+
+Function RegistryDeleteKeyRecursive(regRoot, strKeyPath)
+  Set objRegistry = GetObject(strObjRegistry)
+  objRegistry.EnumKey regRoot, strKeyPath, arrSubkeys
+  If IsArray(arrSubkeys) Then
+    For Each strSubkey In arrSubkeys
+      RegistryDeleteKeyRecursive regRoot, strKeyPath & "\" & strSubkey
+    Next
+  End If
+  objRegistry.DeleteKey regRoot, strKeyPath
+End Function
+
+Function RegistryListSubkeys(regRoot, strKeyPath)
+  Set objRegistry = GetObject(strObjRegistry)
+  objRegistry.EnumKey regRoot, strKeyPath, arrSubkeys
+  RegistryListSubkeys = arrSubkeys
+End Function
+
+Function GetUserSID()
+  Dim objWshNetwork, objUserAccount
+  
+  Set objWshNetwork = CreateObject("WScript.Network")
+
+  Set objUserAccount = GetObject("winmgmts://" & objWshNetwork.UserDomain & "/root/cimv2").Get("Win32_UserAccount.Domain='" & objWshNetwork.ComputerName & "',Name='" & objWshNetwork.UserName & "'")
+  GetUserSID = objUserAccount.SID
+End Function
+
+Function RegistryCleanupSyncRootManager()
+  strSyncRootManagerKeyPath = "SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\SyncRootManager"
+
+  arrSubKeys = RegistryListSubkeys(HKEY_LOCAL_MACHINE, strSyncRootManagerKeyPath)
+  
+  If IsArray(arrSubkeys) Then
+    arrSubkeys=Filter(arrSubkeys, Session.Property("APPNAME"))
+  End If
+  If IsArray(arrSubkeys) Then
+    arrSubkeys=Filter(arrSubkeys, GetUserSID())
+  End If
+
+  If IsArray(arrSubkeys) Then
+    For Each strSubkey In arrSubkeys
+      RegistryDeleteKeyRecursive HKEY_LOCAL_MACHINE, strSyncRootManagerKeyPath & "\" & strSubkey
+    Next
+  End If
+End Function
+
+Function RegistryCleanup()
+  RegistryCleanupSyncRootManager()
+End Function
diff --git a/admin/win/msi/UinstallOldClientDlg.wxs b/admin/win/msi/UinstallOldClientDlg.wxs
new file mode 100644
index 000000000000..f1e54e142545
--- /dev/null
+++ b/admin/win/msi/UinstallOldClientDlg.wxs
@@ -0,0 +1,52 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+ *
+ * Copyright (C) by Michael Schuster <michael@schuster.ms>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * for more details.
+ *
+-->
+<?include $(sys.CURRENTDIR)OEM.wxi?>
+<?include $(sys.CURRENTDIR)Platform.wxi?>
+
+<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi" xmlns:util="http://schemas.microsoft.com/wix/UtilExtension">
+
+    <!--
+         When to change the Product GUID:
+         https://www.firegiant.com/wix/tutorial/upgrades-and-modularization/
+         https://www.firegiant.com/wix/tutorial/upgrades-and-modularization/checking-for-oldies/
+
+         We change the Product Id for every release, to let up-/downgrading always work.
+         But we then should never change the UpgradeCode.
+     -->
+    <Fragment>
+        <UI Id="MigrationDialogUI">
+
+          <DialogRef Id="ExitDialog"/>
+
+          <Dialog Id="MigrationDialog" Width="370" Height="270" Title="$(var.AppName) $(var.PlatformBitness)">
+
+                    <Control Id="Weiter" Type="PushButton" X="236" Y="243" Width="56" Height="17" Default="yes" Cancel="yes" Text="Weiter" >
+                       <!-- <Publish Event="DoAction" Value="RemoveOldClient">updateCheckboxResult = 1 and aquisitionCheckboxResult = 1 and Not Installed</Publish>
+                        <Publish Event="OnExit" Value="success"></Publish> -->
+                    </Control>
+                    <Control Id="Bitmap" Type="Bitmap" X="0" Y="0" Width="370" Height="234" TabSkip="no" Text="!(loc.ExitDialogBitmap)" />
+                    <Control Id="Back" Type="PushButton" X="180" Y="243" Width="56" Height="17" Disabled="yes" Text="Back" />
+                    <Control Id="BottomLine" Type="Line" X="0" Y="234" Width="370" Height="0" />
+                    <Control Id="Description" Type="Text" X="135" Y="70" Width="220" Height="40" Transparent="yes" NoPrefix="yes" Text="MagentaCLOUD durchsucht ihren PC nach früheren Versionen. Sollte eine frühere Version vorhanden sein, so wird sie deinstalliert werden, da sie nicht länger kompatibel ist." />
+                    <Control Id="Title" Type="Text" X="135" Y="20" Width="220" Height="60" Transparent="yes" NoPrefix="yes" Text="!(loc.ExitDialogTitle)" />
+        </Dialog>
+          <InstallUISequence>
+                <Show Dialog="MigrationDialog" After="ExecuteAction" />
+          </InstallUISequence>
+        </UI>
+    </Fragment>
+</Wix>
diff --git a/admin/win/msi/make-msi.bat.in b/admin/win/msi/make-msi.bat.in
index eb14735327fd..29b426e9aabb 100644
--- a/admin/win/msi/make-msi.bat.in
+++ b/admin/win/msi/make-msi.bat.in
@@ -17,10 +17,10 @@ Rem Generate collect.wxs
 if %ERRORLEVEL% neq 0 exit %ERRORLEVEL%
 
 Rem Compile en-US (https://www.firegiant.com/wix/tutorial/transforms/morphing-installers/)
-"%WIX%\bin\candle.exe" -dcodepage=1252 -dPlatform=%BuildArch% -arch %BuildArch% -dHarvestAppDir="%HarvestAppDir%" -ext WixUtilExtension NCMsiHelper.wxs WinShellExt.wxs collect.wxs Nextcloud.wxs RegistryCleanupCustomAction.wxs
+"%WIX%\bin\candle.exe" -dcodepage=1252 -dPlatform=%BuildArch% -arch %BuildArch% -dHarvestAppDir="%HarvestAppDir%" -ext WixUtilExtension NCMsiHelper.wxs WinShellExt.wxs collect.wxs Nextcloud.wxs RegistryCleanupCustomAction.wxs UinstallOldClientDlg.wxs
 if %ERRORLEVEL% neq 0 exit %ERRORLEVEL%
 
 Rem Link MSI package
-"%WIX%\bin\light.exe" -sw1076 -ext WixUIExtension -ext WixUtilExtension -cultures:en-us NCMsiHelper.wixobj WinShellExt.wixobj collect.wixobj Nextcloud.wixobj RegistryCleanupCustomAction.wixobj -out "@MSI_INSTALLER_FILENAME@"
+"%WIX%\bin\light.exe" -sw1076 -ext WixUIExtension -ext WixUtilExtension -cultures:de-de NCMsiHelper.wixobj WinShellExt.wixobj collect.wixobj Nextcloud.wixobj UinstallOldClientDlg.wixobj RegistryCleanupCustomAction.wixobj -out "@MSI_INSTALLER_FILENAME@"
 
 exit %ERRORLEVEL%