I was trying to find a reg key to switch from pro to s mode. cant seem to find it. just playing around on vmware.
Good question. Unfortunately, a computer would have to come from the manufacturer with S mode installed on it. Because of the high security of S mode, users are not able to go from a standard version of Windows to S mode. So, the answer to Your question - You can't find it because it doesn't exist.
15063.0 16299.15 Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\CI\Policy] "SkuPolicyRequired"=dword:00000001 17134.1 17763.1 Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\CI\Policy] "WindowsLockdownTrialMode"=dword:00000001
Yes, that feature has had an unsteady past. Nobody knows what's its fate, in the future. It could simply vanish.