For your system, this PSU would be fine:
http://www.overclockers.co.uk/showp...4&name=Corsair VX 450W ATX PSU (CMPSU-450VXUK)
However, don't go and buy it straight away because it may not be the problem at all.
Yeh, thing is how do I identify the problem if I have done so many things ? lol