I had an issue with my other RAM (2 x 2gb Corsair Dominator) while I was using it on XP, like I said earlier when I was running it with XP I had CPU spikes and it'd cause my WHOLE computer to freeze completely for anything up to 10 seconds.

So I removed it and put in the 4 x 512mb modules (which I'm now using) and it's stable.(So far)

Fingers crossed eh!