First the painfully obvious question: is there a disk in any drive that Windows may be reading as trying to boot from? (My high school english prof would kill me over that sentence) Do you have the drivers for your video card on a cd or floppy? if so, reinstall them. Have you installed any new hardware or software that may be causing a conflict? If so, uninstall and try again. Can you log off and log on (without rebooting) without any problems? I would backup everything you want to keep to cd/dvd before trying the repair install. But you can give it a shot. Personally I have spent more time trying to find and fix some problems than it takes to format and reinstall.
Change the world. Of one person. Today.
If your equation requires either a complex combination of variables to get the desired result OR you can't seem to get the result regardless of the variables....it ain't your variables, it's your constant.