It was not a virus after all. I have no idea what made my old workstation unstable, but after a monster 30-hour scan of its hard drives, all I found was 4 potential threats, none of which was an actual infection. One was a malicious Java applet that never had a chance to do harm because it relied on an old version of the JVM, and I tend to keep my software up-to-date. Another was a 20-year old joke program, pretending to hijack an unsuspecting victim’s computer, which for some reason Microsoft Security Essentials marked as a threat. The third was the user registration program in an old Iomega installation kit, whereas the fourth was the remote control software VNC, which can be harmful if someone puts it on your computer without your knowledge, but that wasn’t the case here.
So then, what was it? My guess is ailing hardware, perhaps the video card. But… it no longer really matters anymore. I’ve done the deed, swapped computers, and successfully set up my new quad-core system to work with essentially all of my peripheral hardware (no mean feat, considering that peripheral hardware, in this case, includes instruments like spectrum analyzers connected via GPIB.)
Now, I can actually get back to work…