That's not logging in as SYSTEM, that's running an explorer process as SYSTEM. Another way to accomplish it in XP & such was by copying cmd.exe over one of the

That's not logging in as SYSTEM, that's running an explorer process as SYSTEM. Another way to accomplish it in XP & such was by copying cmd.exe over one of the default screensavers (which are also just regular programs). When you're at the login screen the screensaver gets run as system, thus giving you the equivalent of a root shell. Launching explorer from it would result in a new user profile being created in explorer and you'd be "logged in" as SYSTEM, but not really.