Affiliate Marketing Secrets

I want to upgrade my brother’s pc and he has the Kingston / KVR667D2N5/1G in his pc. Same as the one on this link.
http://www.misco.co.uk/product/Q65362?affiliate=ram&gclid=CMffj8Ka2LMCFe7MtAodZggAKA
My question is, if I want to upgrade the ram, can I use the 2gb like this link http://www.misco.co.uk/Product/Q128088/Kingston-ValueRam-2GB-PC6400-DDR2-RAM or http://www.misco.co.uk/Product/Q74932/Kingston-ValueRam-2GB-PC5300-DDR2-RAM
The 2gb ones on the link, are there difference with them both? or not?
What would you suggest?