How to Unregister and Register Virtual Machines without Deleting Them

Read the following articles: http://blogs.msdn.com/robertvi/archive/2008/12/19/howto-manually-add-a-vm-configuration-to-hyper-v.aspx and http://msmvps.com/blogs/virtualreality/archive/2009/03/26/how-to-manipulate-hyper-v-vm-symbolic-links-or-how-to-unregister-and-register-virtual-machines-without-deleting-them.aspx