what's the difference between the OEM version of windows XP and the retail version of windows XP. i bought the OEM last winter because it was considerably cheaper than the retail version, a value of about half, and yesterday while browsing newegg, one of the commentors made note that the OEM version gets locked into your motherboard preventing you from upgrading into a new OS like the upcoming vista. is there any truth in the fact that once you install OEM you can't upgrade the OS or no?