Hi,
This error can occur with a support version mismatch between the KMS client and the KMS host machine.
Most commonly we are seeing this when the KMS host is running on Windows Server 2003 or Windows Server 2008 and the KMS client is Windows 7 or Windows Server 2008 R2. An update is needed for the KMS host running on Windows Server 2003 and an update is needed
for the KMS host running on Windows Server 2008 to be able to activate KMS clients that are Windows 7 or Windows server 2008 R2.
This error also can occur when there may be a time difference between the KMS client and KMS host machine.
The error 0xC004F06C listed in the info section may occur if the difference between system time on the client computer and the system time on the KMS host is more than 4 hours. We recommend that you use a Network Time Protocol (NTP) time source or the Active
Directory service to synchronize the time between computers. Time is coordinated between the KMS host and the client computer in Coordinated Universal Time (UTC).
To resolve this problem, Please refer to the KB:
When trying to activate you get 0xC004F074 with description "The Key Management Server (KMS) is unavailable":
http://support.microsoft.com/kb/974998
Roger Lu
TechNet Community Support
