Stumbled upon something by accident. I was trying to remove c:\old.windows from my Windows 10 Professional system to get back about 18GB and none of the administrators command options seemed to work. By accident I brought up a CCleaner application and under the advanced section was a box unchecked called Old Windows Installations. I checked the box, ran the analyze program, and it deleted all of the Old Windows systems. Got back over 18Gb from the old system. Hope this helps someone else with a simple method to get rid of the Old Windows if you have no plans for restoring backwards.