pc won't boot xp

[dickdb]

A friend just called wanting me to help with a computer problem, but I don't have a clue as to what is happening. He has a 3-4 yr.old pc running xp pro. He was reading an email when the computer just shut off. Now when he tries to start it, it will post and show the start up screen but when it starts to load windows, it powers off. Since he lives some distance away, I haven't been to his house to look at it myself, so I can only repeat what he told me. Could it be the power supply? Or maybe a bad sector on the hard drive not allowing xp to load? Any ideas would be appreciated.

[shadowpr]

First thing I would do, is tell him to turn it off, unplug the power cable, and open up the case.

Then he will want to clear out all the dust in there. While doing that, tell him to get a list of all the parts, make and model including power supply.