Windows 7 OA Media

[Rogean]

So we have a ton of computers that come through here (where I work) that have Windows 7 Pro "OA" Keycodes on the side of them, but most of them come preinstalled with XP.

I took one of these keycodes and installed Windows 7 Pro on a pc using media that we get from our volume license login with Microsoft, and it didn't accept it for activation. I had to call in to Microsoft to get it activated.

Can anyone confirm that theres a difference between Windows 7 "OA" Keys and the Business media? Is there a seperate media for OEM That would work with it? If so... Someone send it to me (WHO SAID THAT?!).