Vista SP2 doesn't load past "Welcome"

[Cienja]

A friend's laptop running Vista SP2. I'm XP and this is my first time playing with Vista. Anyway, I can boot into safe mode and can run some programs (I cleaned up the HD, ran SpyBot S&D, etc.) When booting back up, however, I get to the "Welcome" with the spinning icon, and it won't go past there. The hard drive light is flashing, but it won't boot.

Anti virus is up-to-date, etc.

Any suggestions?

Thanks!