I hope Igor, the Windows 98 guru 8), can help us here…

Maybe follow:

  1. Uninstall avast from Control Panel first.
  2. Boot.
  3. Use Avast Uninstall for complete uninstallation.
  4. Boot.
  5. Install again by this command on the folder you’ve donwload and save the install file: setupeng.exe /forceinstall
    Where setupeng.exe is the name of the executable.