I think that you are looking at the next logical step to do a clean install:

  • Download the latest version of avast, 9.0.2011 http://files.avast.com/iavs9x/avast_free_antivirus_setup.exe and save it to your HDD, somewhere you can find it again (if you didn’t save your last download). Use that when you reinstall.

  • Download the avast! Uninstall Utility, avastclear.exe find it here and save it to your HDD.

    1. Now uninstall avast! - using add remove programs, if you can’t do that start from the next step, reboot.- 2. run the avast! Uninstall Utility, it will request it be run from safe mode (and will handle the boot into safe mode), once complete reboot into normal mode.- 3. install the latest version, reboot.

Note: save the copy of avastclear.exe so it can be reused as some users are reporting that after running it, it is self-deleting.