Hello and welcome to the forums. As to your inquiry it's there. Without knowing your OS I will try.
XP...Control Panel...add/remove...double click "avast"...click "change"...click "next"...select or uncheck what you don't want.
Vista and Win7...Control Panel...uninstall...double click "avast"...click "change"...click "next"...select or uncheck what you don't want. Either way don't forget to re-boot.
During installation choose "custom install".
Greetings from the USA.