Hi Jack,

You may have already read this on the forum, but using third-party tools like Revo is not advisable for antivirus software like Avast. Revo is a great software, but for AV’s, it is recommended to use the vendor’s uninstaller tool instead…in this case Avast Uninstaller tool.

If the Repair does not work for you, and you wish to do an uninstall/clean install, please follow these guidelines:

  1. Save a copy of Avast 5.1.889 for the product you need and save it to your HDD:
    Free: http://files.avast.com/iavs5x/setup_av_free.exe
  2. Download the Avast Uninstall Utility http://www.avast.com/uninstall-utility 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. Uninstall v.4.0 and 5.0 in your case.
  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.

Knowledge based article:
https://support.avast.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=504#idt_0003

Once you register with a different email, you should get a full year subscription. Let me know if you have any questions. Thank you.