Also, though, if you upgrade your processor It may and likely will have the same effect as switching motherboards, but it can be remedied by calling M$ and explaining that you upgraded and need to revalidate your key.

Hey guys, thanks for all your help. Could I just ask you if these products will be compatible...well I just really need to know if the following processor will be compatible wiht my motherboard and memory etc.
AMD Athlon 64 X2 4200 Dual-Core Socket 939 OEM Processor

I only have vista home premium oem, will windows allow me to re-validate my key if I change my motherboard?

Your motherboard has Socket 754, and that CPU is Socket 939. They aren't compatible.

Hmm. The site I checked lied to me then

It will work.

Do you think its worthwhile getting a new processor and memory, or starting afresh with an updated motherboard and build up from there?