When you get a popup about an updated version in CCleaner Pro and you click to upgrade, if you get the error "unable to write file" in Windows 10 while it is trying to write the cclearner.exe file, check if you are running MalwareBytes Monitoring. If you are, TURN IT OFF, until AFTER your upgrade finishes. Exiting out of MalwareBytes monitoring and clicking Retry in the update will cause CCleaner to continue to update and complete. Then you may turn MalwareBytes back ON. MalwareBytes prevents CCleaner from upgrading. Best!