Perhaps I should have said "without the advice of an expert," but I mis-used the word "professional" instead. I followed the advice of Cluin (Thread 68739), linked in the post, above, and installed Spybot. I will get around to Adaware tonight.

Something like 250 problems were picked up, the worst, seemingly, was Gator.

Many thanks to Cluin, John in Kansas, and the other "experts" whose advice I have taken from time to time.