What's nice about CCleaner is that it just does what it says. You don't have to deal with functions you don't need, and won't get lost in complexity.
With CCleaner, you load the program, run an analysis to see what the program thinks you can do without, make any changes, and let it go. It's fast and effective.
However, you do have to know something about Windows. For example, CCleaner will clear out all cookies that websites place on your computer, and it will give you a list of proposed deletions that you can edit. However, you need to know which cookies are important.
It's a long list, but fortunately, CCleaner remembers your choices from one use to the next.
CCleaner is able to analyse your registry and remove unwanted entries. Like other products here, it didn't get everything on the first pass - CCleaner found 1029 registry issues, but it took three passes to do so.
Unlike others, CCleaner doesn't provide a report of exactly how much it found, although it does tell you what it proposes to do, and later what it did, useful in case something goes wrong.
CCleaner has capabilities that you won't find in other packages, including the ability to run the program from the command line and to run in the background.
CCleaner also includes a software uninstaller. Microsoft includes an Add or Remove Programs option in Windows' Control Panel. But CCleaner will uninstall programs that Windows won't - a real help when a program is partially uninstalled and leaves junk behind in its wake. The interface isn't fancy, but it is clear.
If you want a package that will do it all, this isn't it. If you just want to get the junk off of your hard drive and out of your Registry, CCleaner will do it - for free.