Three beeps then shutdown

Beep codes vary from one BIOS manufacturer to the next. The number of beeps and the length of the beeps are significant indicators. Here are a few common ones:

AMI: 3 short beeps = Base 64K RAM failure
IBM: 3 long beeps = Keyboard / Keyboard card error
AWARD: 1 long and 2 short = Video error (any other beep combination = RAM)

These codes do tend to vary a bit too depending on the motherboard manufacturer and the version of the BIOS. Check your manufacturer's website for more info if youcan. Also, look in the motherboard manual for some assistance (tech support numbers etc.)

A good place to start though would be to reseat EVERY card in the computer including ram. In fact, remove all of the ram except the minimum amount required by your operating system. Replace the modules 1 at a time until a fault occurs. Then you will know which RAM module has failed. If you still have a fault after reseating the cards, swap the video with a known good unit. These are quick, basic checks that will either fix the problem or indicate a more extensive problem. The problem is likely to be Ram or Video. Good luck with it.

Try this link and see if your board is in there.

http://www.pchell.com/hardware/beepcodes.shtml