Ive done some searching on the web and it seems this problem has been linked to two things, a worm or a bad psu. Do you have anti virus software?

If i were you I would download a free virus scanner like Avast if you don't already have one.

It is odd that it would let you run sfc/ scannow . . are you logged on as administrator? Start -=> Run -=> Command -=> Sfc/ Scanall

Thats the thing about trying to help people over the net, for all I know . .they have a stick of ram improperly seated,
ribbon cables are worn and causing the problem, or the motherboard shorting out all over because they didn't install stand-offs.

If all else fails. . reformat, partition your drive in to two equal parts and install WinXP on one, and Vista on the other.
That way if something go's wrong you won't have to worry about deleting, or fixing the wrong files on the wrong OS.

If you do make sure you run a virus scan before backing up files on your selected media, or else.