The good news - this fixed my immediate problem. The bad news - when I run Malwarebytes and do a full scan, it starts out scanning fine but gets progressively pokier as it goes along (somewhere past the 120k files scanned mark, from what I've seen so far, although admittedly I haven't monitored it all that closely). Using the End Task function of Task Manager doesn't seem to work, and it takes several minutes from hitting Ctrl-Alt-Del to when the option to go to Task Manger comes up, then another few minutes from telling Windows 7 I want the task manager to when the task manager window actually comes up.