You can go to your “Windows” Control Panel for Programs (installs) and under Avast gives you option to “Change”…uncheck GrimeFighter.
If you used the Custom Install it did show this option but most folks just used the standard/defaults install…so “that” is how is how it got on your PC.
There are many threads on the subject…just one: http://forum.avast.com/index.php?topic=145159.0
I personally would never use a one-button cleaner.
Here’s a good thread on this and the theory of use or non-use: http://forum.avast.com/index.php?topic=144993.0