Microsoft Open License Keys
There are now two product keys, Physical and Virtual.
1. Physical: This product key will be bound to the physical hardware the server OS resides on.
2. Virtual: This product key will activate the OS, but not require reactivation if memory, CPU cores, or any other virtual hardware configuration is changed.
Don’t forget to reference this if you need to activate in a vitural world (VMware):
http://support.microsoft.com/kb/949748
