Thanks for your replies.

Thanks S.Z.Craftec - I checked out ‘Hide inactive icons’ and it
was unchecked. Good idea though as I have used it in the
past.

Technical - This is ok. ashDisp.exe is the ‘icon’ …

Yes but there is/are still no icon(s) showing in the tray.
I can still access the program from the start menu and run ‘ashAvast.exe’.

I have from the start suspected it was some setting or service
problem with my XP installation. I’m sure it’s nothing to do with
Avast 4. As mentioned I had this same problem with brand X.

I have to agree with darkparrot. I have experienced strange happenings with the XP firewall. It can and does block services
even from the Administrator unless setup properly in Exceptions
and with the correct scope. But I have done this with all 3 Avast services so it is not likely the problem in this case … ? I guess.

The only place I can think of where someone may know the answer
is in one of the MS newgroups. Any ideas on which NG would be best to
post to ?
microsoft.public.security.homeusers ? microsoft.public.windowsxp.security_admin ?
or ??

Bavnuser