Hello, Please, try avoid using(if any) "" marks while Writing Property Values to the Registry. in your case, provide registry value data as [INSTALLDIR]Sikkermail.vsto for Manifest registry value and check if achieved required behavior. Only for Windows Installer based projects, you can use Windows Installer properties in registry values to store information for later use by your product. At run time, Windows Installer automatically expands expressions of the form [PropertyName] in registry data to the value of the property called PropertyName. Any property defined in the Property Manager can be used in this way. For example, if you would like to store the destination location of your software, create a registry value whose data is [INSTALLDIR]. At run time, when your installation creates the registry value, the data for that registry value is set to the location where your application is installed. You can use the same format for registry key names and value names. For example, if you want a key name to be the name of your company, enter [Manufacturer] for the name of the key. Regards, Chiranjeevi ... View more