Install from scratch:
1.) Download and save to your desktop
avastclear.exe 2.) Download and save a fresh copy of Avast!.
http://files.avast.com/iavs9x/avast_free_antivirus_setup.exe3.) Open Avast! > Settings > Troubleshooting > Uncheck " Enable Avast! self-defense module ".
4.) Uninstall Avast! normally through Control Panel > Programs & feature. Reboot. If you can not complete this step, continue with step # 5
5.) Even if you were able to uninstall Avast! in step # 4, it is important to run avastclear.exe in Safe Mode
How to use avastclear:
http://www.avast.com/en-us/faq.php?article=AVKB10#idt_02NOTE: When executing avastclear, it will ask to be run in safe Mode so follow instructions.
6.) Reinstall fresh copy of Avast! and reboot.
Be aware. Avast! will offer Chrome during installment. Remember to opt-out if you do not want it.After avast! is installed, run a full system scan. If avast! finds something and asks to run a boot scan don't. Report here what was found by avast!