Hmn. Good question. I belive you would need a lower level programmed API, perhaps C? This would require a direct OS call, I belive, and VB6 is good for making cute little forms filled with textbox1, textbox2, and such. Now, if you dig deep, you might find some library with such system call to do it, but I don't know, I never needed such a thing. If I ever needed the computer to restart, I'd show a message asking for the user to do so, and never do it on my own. Never surprise the user, specially if it's a bad surprise like suddenly booting.

Bonus points: make a library on assembly. Why, x86 programming is lots of fun!

EDIT: Ahh ok sorry, I belive I didn't read it fully. But... a login script on VB6? When will it show up? How are you going to start the process?