I have tried using your proceedure:

  1. Download avast! Free Antivirus: http://files.avast.com/iavs9x/avast_free_antivirus_setup.exe
  2. Run this tool in safe mode: http://files.avast.com/iavs9x/avastclear.exe
  3. Reinstall avast! with the downloaded installer from point 1.
  4. Reboot.

Unfortunately, the dialog for avastclear.exe uses a window that is too large to access the function buttons at the bottom. You cannot resize the window and you must click on it’s top program bar to move the window so it cannot be moved high enough to acess the buttons.

This may not be a problem in 7 or 8 but in XP SP3, safe mode has limited video resolution.