After updating to the newest CCleaner 5.79.8704 on Windows 10, I Wipe Free Space anymore. There used to be a checkbox when you clicked on Custom Clean and then all the way at the bottom. But it's no longer there. So I looked up where to find and have found it under Tools then Drive Wiper. So, I choose "Free Space Only" from the dropdown. Then choose "Advanced Overwrite (3 passes)". And then in the box where I can "check" which drives I want to select, my C:\ is grayed out. I don't have any other logical drives mounted--only C:\ Why is it grayed out?