cardiholic 0 Newbie Poster

My friend had a virus and I thought I could fix it. I ran registry cleaner and then ad-aware. After I restarted the computer windows wouldn't start. It just keeps trying to boot but gets to a place where it askes for password. It stays there for a couple of seconds then restarts again. If I try to type his password really fast it says it's the wrong password but it's not. If I don't touch it at all it will keep trying over and over to strt windows but never gets it started. He has windows vista. Also, he bought this computer new at a computer show and he got no disks with it. I thought I might be able to start it with a vista disk but he never got one. Any idea what I should do ? Thanks very much, Jim