Okay Tyler and mikee it should technically effect all version of XP. OEM, and Full. Corp is no longer used since like Eric said it was leaked and over 3 million people had it. MSDN only really uses beta OS's not full version. RC, Beta, and the likes. Vender is OEM. If you bought a full copy from the store it should technically onyl allow 3 instales. I do know what you are saying that you have formatted and it never asks. Same here. I have formatted at least a dozen if not more times and have never had that issue. But it is supposted to be there. I installed XP Home on my other computer, full version which i had bought 3 years ago before i got Pro. And i had to call M$ to get a serial to activate it since the hardware config was different than the one i originally activated it with. So if you use the same system i doubt it happens. But if you try it on 3 different systems you will find that after that you have to activate it. At least that is from my experience. Who knows if you guys will come across it.