Follow this instructions www.avast.com/uninstall-utility
After that download a fresh copy of avast and re install it.
I agree with aventador, scanning several times a day is a bit overkill. If you have all the avast shields on, then you should be fine. But I guess you have your own experience, and it might tell you otherwise.
BTW it is a good idea to exclude avast from SuperAntiSpyware and vice-versa.