New cpu issues help please

hello i am stuck really stuck i have a new AMD Athlon II X2 Dual-Core Processor 255 3.1GHz and when i installed it everything was fine i did a good boot then i saw my graphic card wasn't registration the drivers or or the card. Iv tried rebooting uninstalling the card /drivers but heres the funny thing when i installed the one built into my mb it works. BUt When i put back my original CPU everything is fine any idea whats wrong?

ECS GeForce6100PM-M2
2.00 GB RAM
ATI Radeon HD 4300/4500 Series

( i hope i put this in the right spot)
COuld it be my power supply isnt enough to run both?