Pretty much every Optiplex GX755 desktop purchased and deployed by the College during January 2008 has had Vista activation issues. We believe that this issue was triggered by the recent deployment of Vista Service Pack 1 through Active Directory.
The version of Vista that we use here at UVM is Vista Enterprise. Vista Enterprise uses a centralized license server, called a KMS server, to provide authentication information back to Vista, “authenticating” Vista for another time period after which the computer will again look for the KMS server.
If the computer cannot find the KMS server, the original version of Vista would go into Reduced Functionality Mode (RFM) which is another way of saying that it becomes useless. As of Service Pack 1, Microsoft has eliminated RFM. Instead Vista Enterprise will become nagware, posting endless notices that you may be running pirated software and asking you for a product key. The product key on the sticker on your computer is, of course, for the OEM version of Vista which is NOT what’s currently installed on your computer
The fix for this is to simply provide the generic product key (VKK3X-68KWM-X2YGT-QR4M6-4BWMV), which tells Vista Enterprise to look for the server again and all is well.
Geoff Duke has more information on this on his Blog