Corporations with volume licensing agreement which had been setting up and using Windows Server 2003 has KMS (Key Management Service) server to provide volume activation to computers running Windows Vista and Windows Server 2008, can download an updated patch, KMS version 1.2, to extend support for Key Management Service (KMS) to provide volume activation for Windows 7 and Windows Server 2008 R2, in the event of OS upgrade or acquire of new PC with new operating systems.
The KB968915 update installs Key Management Service (KMS) 1.2 for Windows Server 2003 Service Pack 1 (SP1) or later versions of Windows Server 2003, and will be replacing KMS 1.1 for Windows Server 2003 (KB948003). KMS 1.2 provides support for the following KMS client installations:

• Windows Server 2008 R2
• Windows Server 2008 and Windows Server 2008 Service Pack 2 (SP2)
• Windows 7
• Windows Vista and Windows Vista Service Pack 2 (SP2)

After installing KMS v1.2 with KB968915 update package, new KMS Host Key will need to be installed on the existing KMS host for Windows 7 or Windows Server 2008 R2 client to activate. Once activated, the KMS host will be able to activate all products (depending on the KMS key that is used).

How to Install KMS 1.2

1. Download and install prerequisite Key Management Service 1.0 for Windows Server 2003 or Key Management Service 1.1 for Windows Server 2003, if it is not already installed.
2. Download KMS 1.2 from Microsoft Download Center: (KB968915) 
3. Run the KB968915 executable update file.
4. Restart the computer.

   Note: If you do not restart the computer after you install the KB968915.exe file, you may receive the following error message when you enter the product key:

   Error: 0xc004f050 The Software Licensing service reported that the product key is invalid

After updating to KMS 1.2, administrator has to install and activate the appropriate KMS key from Volume Licensing Service Center: https://www.microsoft.com/licensing/servicecenter/, ensure that incoming communication with the KMS host computer through TCP port 1688 is allowed on firewall, and ensure hat the KMS host computer is published by DNS service location (SRV) resource records to enable automatic discovery for KMS client computers.