Microsoft’s free Volume Activation Management Toolkit (VAMT) helps administrators manage licensing on computers in their organization. Administrators can use the VAMT to update licenses and activate Office and Operating Systems on clients and servers.
VAMT version 3 performs all of the operations that VAMT version 2 did while adding new features. Christian Mohn wrote about VAMT 2 and described its usage in his article, "License & Activation Management with Volume Activation Management Tool (VAMT)." If you haven’t used the VAMT before, check out Mohn’s article to get a grasp of the concepts that are common to both versions
What new features are in VAMT 3?
There are several new features and improvements made to previously existing features.
Active Directory Based Activation -- Active Directory Based Activation (ADBA) replaces the role previously held by KMS hosts in Active Directory. This means that activations are performed in AD itself and is not reliant on any specific hosts.
PowerShell Support -- PowerShell cmdlets replace what used to be VAMT.exe.
Proxy Authentication -- If some of your computers require a username and password to access the Internet, then the new VAMT 3 can serve as a proxy authentication. VAMT makes the connection and routes activation requests through it.
Licensing Reports -- License reporting is built into VAMT, so it’s easy to figure out which computers are not in compliance.
--> Please see the rest on Petri's Website : http://www.petri.co.il/microsoft-volume-activation-management-toolkit-3-improvements-installation.htm