Hi sarah. It does sound like an OEM version. But, as mikey says, i does sound a bit suss. I am running Vista Ultimate that i bought from the shop. I saw the eBay ones and i still bought from the shop for peice of mind. btw... If it is dodgy, Vista needs reactivating every 6 months! So if its ok now, it might not be very soon. And yes, it CAN de-activate itself. Microsoft know if more than one person is sharing a key by how many time an update is downloaded. But, im not saying its not legit. Just tread carefully.