PC won't boot up any advice?

Specifically, it starts up but then comes to a menu with: Start in safe mode, Start in last known config & Start normally. When I select any of them it shows the loading bar thingy for Windows XP but then goes straight back to the menu with the start options again. Last time I was on it I turned it off... show more Specifically, it starts up but then comes to a menu with:

Start in safe mode, Start in last known config & Start normally. When I select any of them it shows the loading bar thingy for Windows XP but then goes straight back to the menu with the start options again.

Last time I was on it I turned it off manually via power button, stupid I know, but I had an exam to get to and the shutdown menu doesn't show up for a while. At the time I'm pretty sure no programs were running in the background, if there was though it would've been the anti-virus. AVG. The computer was also clear of any viruses prior to the problem.

Please help me out,
Cheers
4 answers 4