I recently had to go through this process since we’re using some SharePoint 2010 images for class and they have to run on Hyper-V. I searched online for quite a while, tried a few different procedures (which of course meant rebooting my system 2^32 times), to no avail.
Finally I mentioned it to a fellow instructor and he pointed me to the one and only thing that actually worked. I guess it’s no wonder why he’s a Microsoft MVP. Hats off to Chad Solarz.