Hello rc53_61,
If you look at the back of your old power supply you should be able to find the information you need (if you are going to replace the current power supply with the same one). The best place to find an exact power supply is visiting the manufacturer of your computer system for example: dell, hp, compaq, etc. You can replace a power supply rather easily, the only things you need to make sure is that the plug connection is compatible with the one on your motherboard and the power supply rating is the same or even a bit higher for wattage. Check the following links to find some good quality power supplies at a reasonable rate. These sites will help you with compatibility also by putting in your motherboard information. Let me know if you need further assistance.

Tiger direct

Directron


Just in case the links do not work properly

http://www.tigerdirect.com

http://www.directron.com

If you do not mind, please rate my help I would greatly appreciate it. Thanks