Perhaps you should read how to install the software?

http://www.avast.com/en-us/faq.php?article=AVKB3#artTitle

Always CUSTOM install

http://s26.postimg.org/uqgs839y1/Custom.png

Within avast you can add or remove modules whenever you wish, it takes a few seconds to do so …

http://www.avast.com/en-us/faq.php?article=AVKB96#artTitle