I'm afraid to run cleaner for fear of loosing files that are critical to windows operation. How do I know what options to check for cleaning?
Welcome Superman
There is no Kryptonite in CCleaner to harm you nor your system.
You will find that hazelnut is your Lois Lane and davey is your Jimmy Olsen.
CCleaner does not touch any files critical to windows operation even in its default configuration.
The Registry cleaning function should be used with caution as it could remove a required setting but there is a backup function that should be used to save what it removes.
Hey Superman,
Leave the Cleaner > Windows > Advanced section alone for now.
Have a look at the CCleaner guide to familiarize yourself with the program. (See the link below)
We will be here if you have any more questions.
Also see the CCleaner Beginner's Guide which explains many things before committing to the actual cleaning process.
There is no Kryptonite in CCleaner to harm you nor your system.
You couldn't resist that could you, well I wouldn't of either.