I need to System reset with Vista

Hello,

I've got a problem with my laptop:

Basically i needed to move some data files from an old computer onto this one, and created a new account on this vaio (VGN-FZ21Z), but i stupidly made this new user the administrator and made the previous user second user, which was previously admin.

Now, the computer previously had a Trojan, and i think this is what caused the problem; every time i switch on the computer, it doesn't give the option to switch user from the initial user (which isn't admin), and when i log on, and press switch user, it goes onto a 'Please wait' page and freezes (i then have to reboot it manually). I went to the local computer technics who said that the only option i've got is to sytem reset the computer, but I don't have a disk or anything.

HOW do i do it??!!! HELPP!!!!!