Faulty memory often comes up in posts relating to Win 7 64-bit issues (BSODs, corrupt system files etc), I ran Windows memory diagnostics many times with nary a blip and since 32-bit installed OK without non-repairable sys file corruptions, I assumed all was fine on the RAM front and continued looking elsewhere. Wrong - finally bowed to the wisdom of others and tried a 3rd party app - chose Memscope rather than the oft cited Memtest86+. It showed faulty RAM instantly. A couple of re-runs later on individual modules and with defective one binned, Win 7 64-bit installed faultlessly and sfc /scannow had nothing to report! A bit early to say I'm completely out of the woods, but no BSODs, no stalls and I've yet to experience any Win 7 lags on resume etc plus Windows Explorer is behaving itself admirably. So try a "proper" memory diagnostic app' 1st!