Another curious development: four years ago, soon after I got this computer, I paid for a copy of the WinRAR archiving software and received the registration key by mail. WinRAR worked normally until soon after I installed Avast! -- at which point it started telling me I was using it on a free trial basis and would need to pay for it and register it in 40 days. It turned out that the registration key file, rarreg.key, had disappeared from the WinRAR directory.

I can't prove that Avast! did it (especially since I uninstalled AVG right around the same time) but if the copy I retrieved from my archives (not on the hard drive that Avast! and AVG had access to) disappears again I'll pretty much know whodunit.

I looked at the Avast! users forum and noticed references to (a.) Avast! "not liking" WinRAR and (b.) at least one of the WinRAR sites allegedly allowing malware to be downloaded through it. Even if Avast! has a legitimate gripe with my WinRAR key, though, I want it to warn me before (or at least after) doing anything with it.