While xp pro is running 2 beeps then shuts down

Hi there.
2 beeps is usually a parity circuit failure and is in most case to do with the system memory.
Get a clean, dry, soft paintbrush, remove the power cord, take the side panel off the computer and remove the ram (memory), clean the brass pins on the memory and the slots that the memory sits in with the paintbrush, make sure you get rid of all the dust, blow on the slots when done and reseat the memory making sure it snaps into place and is nice and tight, return the side panel and the power cord and start the computer, hopefully it will stay on for longer.

Please post back with the results and thanks for using FixYa!!

You may have a failing motherboard or power supply unit (PSU) then. Failure of motherboards is usually due to breaking capacitors. A few years ago a capacitor company stole the "recipe" for making capacitors from another company and tried to make their own, unfortunately they did not get the ingredients right and the capacitors started breaking after 2-3 years of use. They sold these capacitors at very cheap prices and a lot of computer companies and power supply makers bought them. This is easy to diagnose. Look for capacitors (caps) (they look like little tiny soda cans) on your motherboard (mobo). They should be perfectly flat on top and not bulged or swelling or leaking anything. There is something in the computer that is overheating or not getting enough power and causing it to shutdown. There are a few companies that will repair broken capacitor issues, if you find that you have that problem. Also if you add a bunch of extra components without upgrading the power supply you can suffer underpowered situations and that can cause internal parts to fail. Have you added any big video cards or extra drives?
And remember a bad PSU does not mean no power, just not enough to run the computer. If you replace the PSU make sure that you replaced it with one of the same or greater output watts. Output Watts should be listed on the outside of the PSU itself.
I would try another PSU first if the mobo caps looked good.