Are you able to get into safe mode at all?
http://www.computerhope.com/issues/chsafe.htm#03
Getting into Windows Safe Mode.
http://windows.microsoft.com/en-AU/w...t-is-safe-mode
What is safe mode?
I had a similar problem as you described in the first paragraph but I was running xp pro, not vista.
Turned out to be some sort of major error which was described as a "loop". It beat me unfortunately.
.
.
.
.
.
p.s. you should have bought a mac.