One of my clients has a Dimension 4300 that is now starting to randomly shutdown. I've checked the power at the outlet, the UPS, it has to be a problem with the PC itself. Doing some research led me to believe that this problem apparently is a known issue. Any known fix? Or should I swap out the power supply?

How much is a replacement power supply for a Dimension 4300? The service tag is: 39NQ011. Also, I'll need a phone number so I can call and order it.