Hi, I'm embarrassed to say I'm a bit confused with this OEM thing... I'd bought an OEM XP PRO maybe a year ago (or more)... haven't had a prob with it, though some people are saying that Vista OEM will cause trouble (don't quite know of what sort) possibly with changing hardware and validation, so thanks for clearing this for me! I don’t exactly know what OEM is… all I know is that the packaging is minimal so is the pricing.