for Windows KMS, you only can have a single Windows KMShost product key on a single KMShost.
This is why it's important to choose the correct key :)
Windows KMShost pkeys, when loaded onto a WindowsServer OS, will issue activations for all editions and versions at the loaded level and also below that level, including Client editions (eg Vista/Win7/Win8).
So, if you have loaded the WS2012 KMShost pkey, you can activate everything below that.
It is not possible (nor necessary) to load more than one Windows KMShost pkey on a KMShost.
Also, the KMShost pkey chosen, must match the OS of the KMShost machine, i.e., you can't load a Win8 KMShost pkey onto a WS2012 machine.
Office KMShost pkeys are very different to Windows KMShost pkeys. Office KMShosts are version-specific, and do not activate down-version clients.
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