There are a couple of problems here: Windows and Windows\System32 are system folders, so access to them is not guaranteed - and if you can't access the folder, you can't access the application. Start by checking the permissions that the user your app will run as has to access the folders.
Secondly, what you want to do is rather strange: restoring your system from within a application is an odd way to behave.
Though if I try it:
string path = Path.Combine(Environment.SystemDirectory, "rstrui.exe");
Process.Start(path);
It works for me - and I press Cancel immediately! :laugh: