Frankly you need to read and heed the Tip when you post a question. For review:
"Tip: If you are asking for help to troubleshoot a computer-related problem, please be sure to include all the necessary information (ie: operating system, model number, hardware, software, etc) that will help others identify your problem for a speedy resolution."
In your case, nothing about what you have was noted. To many new PC builders they often choke on the fact that today's 2GHz and up wonder boards require 450 Watt power supplies or have orneous cooling requirements.
Inventory what you have, reveal what you are thinking about putting in and the forum can critique it.
Bob
someone donated a system and it has several problems with it. Instead of trashing it, I want to rebuild it. Like new motherboard and stuff. The problem is that I have the faintest idea. So I am starting fresh. How do I know what type of motherboard to get. I am going to start with the motherboard. I figured with all the expertise on this message board, we can rebuild together. Once it is completed, the system will be donated to an afterschool program. Will you guys help me rebuild the system?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic