Thanks for the quick reply.
Cheers for memtest too, heard its good. And I am quite familiar with burning ISO's =].
I have a program called speedfan. Heres my temps:
Local: 31C
Remote: 28C
HD0: 26C
Core: 49C (goes to 79C when playing WoW).
Im not too sure whats too hot etc so if you could fill me in anyone?
Also, I have just bought a surround sound system for my computer which has 5 speakers + Subwoofer. I'm thinking that this may be causing the lockups by taking too much power from the power supply? Any advice on that?

(btw its plugged in at the wall and only connected to my PC through the sound card).
Thanks in advance!