Avast Clear (Avast Software Uninstall Utility) can completely remove Avast when the Add/Remove programs option does not work properly.
How to uninstall Avast using Avast Clear (Avast Software Uninstall Utility):
Download aswclear.exe on your desktop
Start Windows in Safe Mode (reboot, tap f8)
Open (execute) the uninstall utility
If you installed avast! in a different folder than the default, browse for it. (Note: Be careful! The content of any folder you choose will be deleted!)
McAfee Consumer Product Removal Tool is designed for the complete removal of McAfee Security products in order to reinstall or install a different antivirus.