Activating Windows servers to KMS server

For people who use a Key Management Server (KMS), you don't need to fill in a serial number and activate with Windows 7/2008/2008R2 directly, but you use a separate server for this.

On the server you need to activate, open an administrative command prompt, and type:
slmgr.vbs /skms <kmsserver> (the part between brackets is the kms server in your organisation)

It will pop up a message saying the KMS server has been set correctly:

After this, type: slmgr.vbs /ato

If all goes well, it activates the server:

You may encounter an error:

 

 
In this case, check the following:

• Can you ping the kms server?
• Can you telnet to port 1688 on the kms server?
• Is the time and date set correctly on the server you want to activate?

 I had the last one today, and forgot to check the date. The time was set correctly, but the date was 2 months off(doh!).