Thanks for the assistance but it turns out that my problem was unrelated to uninstalling the PC Tools firewall. Because I was unable to log into Windows, I could not try what the links that you found suggested.
In desperation, I just taped every key, turned every switch off and on, and as a last ditch effort, unplugged my Logitech wireless mouse USB receiver. That stopped the ringing and the unassisted keystroke entries. Once I was able to log-on to Windows I checked my device manager and everything seemed in order.
My next step was to take the Logitech wireless mouse and try it on my desktop computer. Same problem. I then removed the batteries to see if that had any effect. It didn't, even without power to the mouse, I had the same problem. I don't know if that means the receiver is picking up some kind of interference signal or what, so tomorrow I plan to take it to work and see if the problem replicates itself there on one of my work computers. If it does, I suspect I need a new USB wireless mouse receiver.
I haven't had a chance to see if I can find aney other reports on the internet about similar issues with USB wireless receivers. I'v had it for several years and it has worked just fine up until yesterday.
Thanks again for your help.