If you do not know what you are doing the REGISTRY MUST NOT BE CLEANED.
That takes you into a whole new world of hurt,
and is known to clean items that are recognized as redundant,
and to omit cleaning of items which are still in use - just as it should.
UNFORTUNATELY some keys that ARE in use may be used by registry key XYZ,
and when XYZ is removed then the key that had been related becomes redundant and will be zapped when the registry is next cleaned.
I always clean the registry a second time to confirm that no "new" redundant keys are available to purge.
I rarely find anything - just once was enough,
but some people may need to purge 3 or more times before nothing else is found.
You would be well advised to refrain from touching the registry.
If you use the file cleaning section and ANALYZE you get a summary of what will be removed.
If you right click on that screen then choose "save to text file" you can accept or modify the default location,
and the saved file itemizes what will be deleted.
then hit the "Run Cleaner" button,
Then ANALYZE and save text again (to a different file)
The second file WILL tell us exactly what was not deleted at the first attempt.
The first file MAY be useful to show if CCleaner failed to see the above the first time round,
or if perhaps there is some restriction upon your ability to authorize deletions.
Attach these two files to your next post for further guidance.
Alan