This might help you deal with the issue: https://blogs.msdn.microsoft.com/dau-blog/2012/02/28/mouse-not-captured-in-remote-desktop-session-when-virtual-pc-vhd-file-runs-in-hyper-v/

Try to reinstall the virtual PC tools. Once it is done, make your guest to use the changed hardware. Here it is described how to accomplish this without a mouse: https://blogs.msdn.microsoft.com/dau-blog/2012/02/28/mouse-not-captured-in-remote-desktop-session-when-virtual-pc-vhd-file-runs-in-hyper-v/

Hope it helps.