There is one minor cleanup step that you can do. Search for all files with the exact matching text pattern:

*.REN

Delete all such such files that Blacklight had found and was allowed to rename.

It feels like my computer is probably the best it can be without a complete formatting and re-installation.

I suspect we are as far as we can get with your PC. Please continue to run all the scan tools (that you are now familiar with) to maintain and monitor your PC's current functional state. I personally run at least one scan tool daily.

Thanks for the excellent and relevant feedback throughout this process.

I could not do System Restore because that function is not installed on my computer and I don't have the installation CD to install it. (I have the authority, just not the software.)

Sorry, my mistake - since you have W2K, there is no 'System Restore' feature like that described for Win XP.