Hi everyone,
Thanks for your replies to my initial question. I now have managed to get the UI to load and run... I followed Eddy's advice! All I did was to reinstall the operating system (XP sp3) but this time I used an XP Professional license and not the XP Home Media one that I used before. Then after re-installing Avast, I found that it now works perfectly.
Weird, or not, it worked for me.
All the best, and once more, thanks.
Ken