Although it is against the terms of the licence to move an OEM version of the software to a different PC, as the licence was for use on the original PC only, I have done this successfully.
Whether you have to call the activation centre or not may depend on how many times the software was loaded / reloaded on the initial PC.
Of course you can only use OEM software where you are going to support it, and where you are a system builder, in other words you have made some changes to the hardware. That change can be as cheap as installing a new Network Card. Since spending £10 on a new NIC enables you to buy legitimate M$ OEM software dramatically cheaper than the retail version, it seems like a good bargain to me
Of course how M$ know that youve upgraded the box itself I don't know, unless M$ windows is in fact spyware
