I updated today to latest pro version.
Noticed it took a long time to examine previous windows install files.
Now have problems with display driver.
Are you referring to Windows.old?
If you let it delete the Windows.old files that has been known to cause issues and break something for some people over several years, although there's only been a handful of posts about it. Some users have figured out if you want to clean Windows.old files it's safer to use Disk Cleanup which is built into Windows.
I will point the admins to this topic as another source that deleting Windows.old is causing an issue for some people.
There have been reports of this afecting Windows 10 for a while.
It's best not to use CCleaner to clear windows.old with Windows 10.
(I believe it's been removed from the latest CCleaner versions?)
You may find the new 'Storage Cleaning' in Win10 1803 faster than using disk-cleanup.
You can find it at:
Settings> Sytem> Storage> 'Free up space now'.