Win 7 Activation

I recently upgrade from XP to Win 7. Did so on 3 computers. One now keep's
giving me this message that "Windows 7 could not activate" then upon clicking on it give's alternatives to activate, phone, re-enter product key. I re-entered the key 3 X to make sure it was right, and was told it was not the right key, this is the same key I used to upgrade to begin with and have two other computers working with this key. Windows is operating normally but why this message? I am afraid that Win 7 might stop working if this is not resolved. T.I.A. for any help.

 

Correct me if I'm wrong here, you used the same key on all 3 machines? It sounds like you don't have multiple copies of W7. It's one machine per copy unless you got a pack and that's out of my league to answer.

 

have you tried calling it in? If i remember correctly, it's just an automated phone system, and might help.

 

Did not know it was good for only one computer, Used my Vista disk to upgrade the 3 computers from Xp before I upgraded to 7.