Ok, I've done research and still confused on this whole thing. The whole OEM License of windows is confusing. So here is the situation. Years ago, before boot camp, we needed to run Windows for a few different appys, so a friend of mine built us 2 small shuttle systems for our business with OEM versions of XP. Those should be valid licenses as they were sold to us, the end user. We don't use those comps anymore, but I'm wondering if I can use those versions to qualify for a upgrade. We have 2 15" macbook pro's we want to install win7 on. Will the upgrade work for this? or is it not valid since it will be on a different machine?