New Memory and a new CPU ordered

The motherboard arrived yesterday and I fitted it last night. No luck; still in the same place. Mind you, with all the components I’ve bought, I should be able to make another computer from the parts I’ve bought to replace the old ones and make someone else a nice computer.
I’ve ordered a new CPU and memory. I’m winding my way around to the opinion that it’s the CPU. It must have overheated from the first 2 weeks of use. Even without a smidge of overclocking. Maybe it has something to do with the 9800GTX cpu sitting immediately below it?
The replacement CPU is a slower, quad-core processor, and if the memory isn’t shot will mean that I’m up to a chunky 8gb of RAM on 64bit vista.
C’est la guerre. It’s only money.