While trying to use Spybot to search my system I kept getting an XP popup warning me about a threatening virus or infection. The trick was that the site wanted me to buy a year's subscription to its service. It was a persistent pop-up, and only disappeared after I completely re-booted my system, but it's apparently out there, and I suspect that it's a worm or some such. Using Spybot and Avasti to scan my system, no infections were found, so I think this thing was a bad one. I'll have my tech try to find and delete it, but Windows XP regularly inserts updates into the system and so there are, over the period of a year, dozens of such ones, and it's hard to figure which of these, if any, was responsible for the problem.