Process.Start(osk.exe)

            var path64 = Path.Combine(Directory.GetDirectories(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Windows), "winsxs"), "amd64_microsoft-windows-osk_*")[0], "osk.exe");
            var path32 = @"C:\windows\system32\osk.exe";
            var path = (Environment.Is64BitOperatingSystem) ? path64 : path32;
            if(File.Exists(path))
            {
                Process.Start(path);
            }