Going nuts over this P4 HELP!

I bought a new P4 2.4 cpu and a soyo board.
It booted ok for 1 week and then quit so I took it back to the store
and they said bad cpu and gave me another one.
Then I installed it and same thing no boot!
I triple checked everything piece by piece to make sure it wasnt me. So back to the store again and they say its my mobo and power supply,
so They give me another new p4 2.4 and I buy an Abit mobo and a 400 watt
Ps.
Works for 1 week and then back to square 1!
Somebody please help.
Thanks,
jsm:confused:

Could you list the specs of this system. The brands and models of the parts would be quite helpful.