error while installing sp2

when i try to install sp2 i get a message that

" The product key to install microsoft windows may not be valid " .

 

The product key you are using most likely is either illegal or it may be a corporate key that has used all it's licences. We use a corporate key here and after the given amount of installations have been done, the key is no longer valid.

You can call microsoft and they will update the corporate key (if you have this one). If this is a single home user product key and it's a legal copy, you can call microsoft and they will give you a new one.