This article provides the information on "License Pools for Windows Images Using Microsoft Key Management Service (KMS)".
The customer expresses a need for imaging a large volume of client systems without inputting a Windows product key for each system.
The Microsoft Key Management Service (KMS) was developed for this purpose. Conceptually, it operates similarly to a DHCP server that leases IP addresses. A KMS host server on the local domain can provide licenses from a pool to the client systems.
The following MS Technet article provides an overview of KMS: http://technet.microsoft.com/en-us/library/ee939272.aspx
A guide for KMS planning and processes can be found here: http://technet.microsoft.com/en-us/windows/dd197314.aspx