Avast Slowing Down Internet - Advice Please

Hi, I am new to Avast and only downloaded it last week and am pleased with it; however, it definitely seems to me that it has considerably slowed by internet surfing (IE - latest version). I disabled the Webrep but I wonder if anyone could tell me if there is anything else I should be changing in terms of shields or whatever. I have basically left the settings as they came, so to speak.

Any help is much appreciated and thank you.

what AV did you have before you installed avast! ?
have you removed it ?
have you run a removal tool to clear all leftovers ?

run and reboot - removal tools http://thewebatom.net/uninstallers/security-software/

Prior to Avast I was using C.A. and I have run a removal tool…what should I be doing?