You guys a little off, well some of you. There is NO difference between an OEM disc and a retail disc, except for the packaging and you get 3 months free tech support from M$ with a retail copy. All LEGAL copies still require the activation key, and can only be installed on one PC. The discs you get from dell/gateway, etc. are OEM system restore discs, and they cannot be used on other PC's, as the software checks to make sure it is actually a dell/gateway PC. An OEM disc bought (and an IDE cable counts as hardware) from like newegg (US) works fine on ANY PC. OEM copies are half the price of retail, and I've used several XP home/pro and 2000 oem discs on PC's I build for people. An OEM disc works fine, same goes with Norton's, nero's, and many other OEM discs.