Check this link for the uninstaller tool:
http://kb.eset.com/esetkb/index?page=content&id=SOLN2116

…then reboot your machine after doing any uninstall.

After this, you will need to uninstall Avast and do a clean install:

  1. Save a copy of Avast and save it to your HDD:
    http://www.avast.com/download-software – all versions
  2. Download the Avast Uninstall Utility http://files.avast.com/files/eng/aswclear6.exe and save it to your HDD.
  3. Disconnect from the Internet at this time.
  4. Go to Control Panel and uninstall Avast through Add/Remove Programs if possible and reboot.
  5. If Step 4 fails, boot into Safe Mode (hit F8 repeatedly) and run the Avast Uninstall Tool.
  6. Reboot.
  7. Install the newest version of Avast and reboot.
  8. Get Internet access and register your copy for Free:
    Free – http://www.avast.com/registration-free-antivirus.php
  9. Update the Avast definitions.

Let us know if this fixes your problem. Thank you.