Breakthrough, which was aided by your notes. I went to CCleaner folder on "C" drive; manually loaded the CCupdate.exe and it failed with permission issues. That wasn't intuitive, since the OS is Windows 10 (64-bit) latest updates. However, the laptop has not been active for a few months which caused many OS updates to be loaded. I reviewed the error messages from CCleaner Pro installation, then changed (fiddled with?) Windows 10 permissions. Next, I downloaded the Free Trial version of CCleaner Pro (64-bit), and manually installed it. I tested the installation by running the "Analyze" option, and it worked!! Next, I checked Options > About and CCleaner - ProfessionalEdition; Registered to: Me; v5.65.7632 (64-bit) is displayed. All is well!! Thanks for your support.