After trying to troubleshoot why crysis was crashing, i did what people on here suggested and Tried putting the RAM in 2gb at a time. However, i did this, and the 2nd ram sticks failed to boot. I put all 4 sticks back in - Vista boots up only reading 1gb of ram, even though there is 4 sticks. I have 2 sticks in now, and it is only running one.
Could it be that i've blown 3 sticks of RAM!? I do hope not, I already feel a voice in the back of my head shouting 'If it's not broke don't fix it'