to wipe a drive can take hours, if you reboot Windows and forgot that the drive wiping process is still running in the background, windows should ask like in unsaved textdocuments, if you really want to reboot. At the moment windows reboots without asking. This is my suggestion/feedback for ccleaner.
Absolutely Ridiculous. 3TB drive 70% wiped, approx 3-4 hours left to completion and W7 did an auto update and rebooted. Why didn't the software prevent the reboot and wait until Drive Wiper had completed? I should be shipping the drive today and now I can't. What was the update? Office, not exactly a life-changing update. Now I'm using Eraser software instead, fingers crossed this software has a little more discipline. Just Ridiculous.
In my experience, if Windows Update wants to do a reboot, and you fail to respond to the "will reboot in 10 minutes - postpone or reboot now" prompt then it will do a force shutdown, regardless of what is running.
I think we have all been burnt by this undesirable feature at some point.
Probably best to stop the Automatic Updates service if using Drive Wiper or Wipe Free Space. If I use Wipe Free Space I always stop the Automatic Updates service - although it would be nice if CCleaner could automatically do this for us and possibly also stop other interfering services or programs.