>It could well be due to a number of things, but one of them, is a recent bad driver install. If you installed any drivers recently, like the last time you used it, I would uninstall that driver. Secondly, it could be a bad RAM stick. Have you attempted to switch RAM or have you gotten into the computer at all and messed around with things? If you took the RAM out or even butted up against it, you could have loosened it and this can cause that problem.
You have to have your restore disk(s) or a full version of the operating system. If there is nothing on the computer you are concerned about, then why not just attempt a restore point first and see if that doesn't do it? If not, go ahead and just reinstall as long as you have the correct restore disks. If restoring the operating system or reinstalling it doesn't do it, then you know it is hardware related. You may even run into problems trying to reinstall if it is hardware malfunctioning.