AS a side note, let's not overlook the obvious either. This may be an electrical problem caused by the CPU needing to have the cpu cooling fan cleaned out. Perhaps even taking off the cpu heat sink and cleaning off the old thermal paste from both the heat sink and the cpu and then applying a new coat of thermal paste.
You might also need to clean out the psu with some compressed air and then check the voltages thru the bios.
Blow out the entire case while you are at it - too. Having fuzzy domestic critters in the house makes this a mandatory chore and many neglect to do it - as this is proper maintenance anyway.
Make sure the video card is properly seated and clean the contacts along its edge and use some 'de-oxit' in the card slot too. Clean all contacts with air and inspect for contaminants!
Once that has all been done, you may need to download a disc check program on another computer and test the main drive. We think of drives as having unlimited lives. But frankly - that just isn't so.
[COLOR=#000000][FONT=verdana]“Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying the wrong remedies.” Groucho Marx[/FONT][/COLOR]