I'm pretty sure you can only do that kind of thing if you're already an admin on the machine. If you are, the same trick works on all windows versions of the NT lineage (NT, W2K, XP and later).
But if you're not an admin, you don't have the right to add a user. In that case, you need to google for a product that lets you boot off a floppy or a CD into some kind of unix. From there you can reset the admin password to blank (they let you choose a password, but blank is the only one that actually works). When I say blank, I mean no password at all. Once that's done, remove the media, reboot, and you can log in as admin and no password.
For the sake of security, change the password and don't forget it !! Some things can't be accessed without having a proper password, so you'll probably have to do it anyway.