After installing the latest (1511) update to Windows 10, I ran Disk Cleanup (with System Files option) to delete the old stuff It never stops! I've let it run for many hours. I am able to cancel the operation, and when I reboot and try it again, it shows little space to regain, so it must have done its thing, but if I run cleanmgr again, it once again just never terminates.

Is there a fix for this?