Kevin Remde explains how Hyper-V in Windows Server 2012, Hyper-V Server 2012, and Windows 8 allows the addition, removal, or configuration changes of some key aspects of a virtual machine; even while it’s running.  Others, however, are still not able to be changed.  And often, the ability to make changes may also be determined by the capabilities of the operating system running in the impacted virtual machine.

Read on…..

http://blogs.technet.com/b/kevinremde/archive/2013/03/05/you-want-to-hot-add-what-20-days-of-server-virtualization-part-2-of-20.aspx

Kick the tires on Hyper-V within Windows Server 2012 at http://aka.ms/msproducts