Hi David,
Thanks for responding to my post.
On that unit I am running Win7 Pro 32-bit SP1. The version of the Free Antivirus is 21.5.2470 (build 21.5.6354.679). I am not getting any error messages under normal operation or during any installs/reinstalls that I have done.
I expect the interface to be slow on opening with that ancient CPU, but this is much longer than normal. When either double-clicking on the minimized icon in the notification area or right-clicking the icon and choosing 'Open Avast user interface', I initially see the interface start to load with a white box, and then nothing happens. As I'm sure you're aware, that box then turns a dark color, then the interface loads (which works fine on my other considerably more up-to-date units that have the same version installed).
Prior to updating/installing/re-installing to the current version, of course things would run considerably slower, i.e. scans and manual updates.
Cheers,
Mike T.