Hyper-V Program Manager
It is possible under Hyper-V to get into a state where you have a virtual machine that is still running correctly - but does not show up in the virtual machine list under the Hyper-V management console. The two most likely causes for this are:
In my case the xml file gotten filled with 'null' characters. The machine is still running (can ping, remote desktop) but that's about it:( how can I get my machine back?