Thank-you for all your excellent responses. Here's what I've figured out. (I'm NOT a techie.)
- I uninstalled and then reinstalled the software and the Tray Icon has reappeared.
- there's a start-up item called "ashDisp.exe" that I had deleted and it is the program that creates the on-screen display (OSD) including the Tray Icon. It seems that disabling this item does not affect the software's ability to detect viruses in any way, shape or form. It seems that the only thing that happens is that you no longer get the OSD - i.e. Tray Icon, notification boxes of viruses being detected, database updates being processed....or the nice voice telling you the same. However, as an example, when a virus is inside an email message, even though you don't get the OSD, the virus is stripped from the email and a message is inserted stating such - provided, of course, that you have the software settings set-up to do so.
- I'm not a big fan of having unnecesarry processes running in the background chewing up valuable system resources. However, ashDisp.exe seems to use up only about 2MB of memory on my Windows XP machine so I'm likely just going to leave it running - even though it appears to be unnecessary. (I get a kick out of the little voice saying "Your virus database has been update" and you don't get that when you turn-off ashDisp.exe!!!)
- I also really appreciate the avast! External Control program. Thank-you so much for providing it and letting me know about it
Dave