DavidR makes good points....and for FYI Avast 8 is listed in 4.13.4693 version....see pic.
Also, many opinions but you should also make sure CCLeaner does not clean some of the windows items like mem dumps, logs, etc....see pics.
I CAN tell you one thing I use CCleaner for is the uninstaller section.
I can tell you I had nasty problem with JAVA and after trying to deal with a corrupt install only CCleaner uninstall section (in tools) was able to....and easily...remove. Life Saver.