virtualbox.org

When a VM freezes for whatever reason, I cannot end the process to free up the huge block of memory it is taking. Ending with task manager or process explorer returns an access denied error. I can't even restart my computer normally, I have to force restart with the button on the PC or the screen will hang on 'restarting windows'.
Any way to terminate a VM process once its frozen?

I've never had that problem with VirtualBox, so I pass. Perhaps you should ask on a Windows forum, since I'm not aware of any systemic VirtualBox problem. Perhaps you should try a memory check, - and a disk check, since frequent power cord pulls are not likely to improve the filesystem integrity.