How to activate Windows 2008 or Vista
Windows 2008 or Vista Business or Vista Enterprise can complain when you try to activate. This is especially true if you haven't installed a key during installation.
Microsoft recommend 2 routes to solve the problem,
1) Setup a KMS (Key Management Service). If you want to go this route, read this Microsoft article:
http://www.microsoft.com/downloads/details.aspx?FamilyId=9893F83E-C8A5-4475-B025-66C6B38B46E3&displaylang=en
2) Install a Multiple Activation Key (MAK) and then activate Windows as normal.
For option 2 follow this method:
1) First, go and look out your MAK. Its a 25 character key in blocks of 5 like this xxxxx-xxxxx-xxxxx-xxxxx-xxxxx If you're using ISV, Action Pack or MSDN versions you can get the keys online through the MSDN portal.
2) Go to the server and start a command prompt: Start> then type CMS in the search box and press enter.
3) You should now see a command prompt flashing c:\>
4) Type: slmgr -ipk xxxxx-xxxxx-xxxxx-xxxxx-xxxxx then press Enter. Replace the x's with your own key.
5) There will be a short delay, then you should see a popup window telling you that the key was installed successfully. If it doesn't, check you typed the key correctly and repeat the above command.
6) Now, click Start> then right click Computer and choose Properties. Find the activation link near the bottom of the window and activate windows. That's it!