Yes, but make sure you earth the Pineapple first...
Other obvious things to check are that all your cards - memory, graphics etc are seated properly & have no dust on their connectors. Also that there is no dust clogging up the pc in general, especially around the fans & double especially around the psu fan.
Also, try to look in event viewer under the system tab. Imho, event viewer in xp is far easier to peruse than in Vista or 7 & can yield a wealth of information - if you can tie system events to the times at which the pc dies, you may well be on to something.