So what haven't you swapped,
cpu video and
ram? Can you try with just one DIMM installed, and do you have another
CPU to test? If it's the Q6600, which I believe it is, that should be fine for any P45 board so doubt it's a BIOS issue.
Do you have another
cpu, another video card? Maybe another stick of
RAM? Does your
ram require a higher voltage than the stock 1.8?