Question : Which KEY do I use for my KMS Server and clients?

I have installed Windows Server 2008 R2 Standard, and have used a Windows Server 2008 R2 Standard KMS B key to activate it. Also I have installed Office Professional Plus 2010 Key Management Service Host and have put the key in.

I have run the cscript slmgr.vbs /ipk xxxxx-xxxxx-xxxx-xxxxx-xxx (Windows 7 KMS key) and cscript slmgr.vbs /ato on the Windows 7 Client but its failing as its saying Error: 0xC004C008. The activation server determined that the specified product key could not be used.

Have I used the wrong key on the client because reading on Microsoft site, an article says I need to call Microsoft as I might have used all of the subscriptions?

Hope you can help. Thanks

Answer : Which KEY do I use for my KMS Server and clients?

Usually you are allowed 10 KMS hosts with a single key for load balancing and what not. Your Windows 2008 KMS B key will be able to activate both Windows server and Windows 7/Vista clients. The Windows 7 KMS key would be used to setup a KMS host that can only activate Windows 7 machines.

I would try registering the KMS key on the Windows server and see if it will go.