Hi guys, can anyone help me please?

I've just swapped out my E6600 for a Q9450 and updated my BIOS to 2801. I'm trying to install Vista but I keep getting 'memory management' BSOD and sometimes it just restarts after a BSOD (too quickly to read the exact errors).

I've ran the Memory Diagnostics tools and it says my memory is fine. I even replaced the RAM with another pair but still it crashes. I was reading this thread and someone suggested trying to increase the voltage on the RAM so I increased it to 2.0v but still no joy .

Is there a way of knowing whether it's the CPU or the BIOS that's causing the problem?

So far I know it's not the GPU, RAM or HD.

I'm using:

P5W DH Deluxe (2801)
Q9450
2GB OCZ
320GB HD
7800GTX

Thanks in advance guys!