It could be a few things causing this. Which CCleaner version are you using BTW? One that seems to be a regular culprit is a corrupt recycle bin. It happens and is fairly easy to fix: https://forum.piriform.com/topic/42673-corrupted-recycle-bin-fix/ Some have reported that running Windows built in Disk Cleanup will often clear whatever System File blockage it was that was causing CCleaner to take so much time, and CC runs more quickly afterwards. Run Disk Cleanup once for 'normal'