Hi Carmel,
Sorry your having problems and welcome to the Forum.
Part of your problem is that Norton AntiVirus is not compatible with Avast! Wich means NAV has to be removed from your system. Unfortunately, just using the add/remove programs function does not remove all of NAV. The only way to do it is to go to the Symantec website and download their special program for deleting NAV.
Your second question reguarding Internet Explorer:
No you can’t totally remove it from you system. it is needed to do the updates for your operating system.
Hope that helps.