OEM has a license to install on one machine.
Retail has a license to install on one machine as many times as you want.
If your PC build changes significantly, Microsoft counts this as "another machine" and may refuse to activate your copy of Windows on it, BUT this has never happened to me.
Generally speaking I'd advise you to get the OEM version.
ZombieKiller7
Not "as many" machines as you want, but more than one. Typically the number of activations you get is somewhere between 3-5 distinct hardware configurations. That being said, in the case of both OEM and Retail if you run out, all you have to do is call Microsoft and give them a reasonable explination for why you are activating again and they'll almost always do it.
To the Op: No, buying OEM is not illegal in any way. The distributor/retailer selling the OEM copy of Windows will typically be required by their agreement with Microsoft to not sell the OEM copy unless they are also selling hardware with it, but that doesn't mean you have to necessarily buy a PC. Often the agreement specifies -any- hardware so you may need to also purchase something as little as a power cable.
-Byshop
Log in to comment