I was building a new Server 2008 machine for a customer a few weeks ago. After installing the OS, I decided to activate the OS. I was told  I would have to activate over the phone because Internet activations do not work from the office. Before I could activate though, I needed to change the product key to the customer’s key. When I typed in the new key, I received an error stating “Invalid product key”. I decided to call Microsoft. They verified the key was correct several times in different departments. I was told it might be a key/media mismatch. So I reinstalled and immediately tried to change the product key again. It again gave me the same error. I was finally told that keys generated after SP2 was released would not be recognized as valid until the system was running SP2. I installed SP2 and the key activated without a problem.