Originally it seemed that it crashed when I opened a web page in Firefox. Not every time, not always with the same page. Just now and then. So I tried using Internet Explorer for a day, and with no crashes so I figured the problem was with Firefox.
I updated to the latest version of Firefox that I'm using, and that didn't help. So I went back to Explorer, and sure enough, it caused a crash when I opened a web site (again, not immediately, and not on every browsing session.)
So I moved to another computer to do my web browsing, and managed to have a crash while I was using Word. So it's not tied to a browser.
If I"m not doing anything on the computer, it doesn't crash. This computer (in fact most of my computers), is powered up all the time. That suggests that it's not a hardware problem, though I did run a memory diagnostic overnight and that passed multiple times.
I use AVG anti-virus regularly, and ran a scan with that with no problems found, so I hit the web to try some other virus and malware scanners. The Microsoft scanner didn't find anything. I tried Sophos virus remover and that run once, showing three malwares of which it cleaned two and said it couldn't clean the third. So I tried to run it again to see if it would do better next time and it wouldn't run. It stops at the point where it checks for updates and says "could not access network location data." The same download runs fine on another computer (on the same network). I stopped Zone Alarm (firewall) to see if that would let it get to wherever it wanted to go, but that didn't work either.
I tried Kapersky and that didn't find any problems either.
So now I'm running SpyHunter and it's displaying hundreds of adware cookies (to be expected if you go on the 'net) and hasn't found any real malware yet, but it keeps giving me a suspicious popup message that doesn't make any sense to me:
"SpyHunter has detected that some Windows components are disabled . . . blah blah blah." In the window where it lists the disabled components, there's only one - System drives. What??? If the system drive is disabled, how can Windows run? There's a button inviting me to restore it, but I don't want to do that until I understand what this means.
I suppose it's as incomprehensible to you as it is to me, but if you have any thoughts, let me have 'em. My next step is to open up the case and see if any of the fans aren't working (overheating?) and wiggle all the power connections. You know me and my cheap, old computers. I'm thinking of going to the local computer junk store and see if they have another one enough like this one that I can swap the clone disk drive into it (which I might try doing with the existing computer when I open it up). If that crashes in the same way on a different chassis, I can probably assume I really have a problem with something on the drive.
Fortunately, everything I need is backed up on another computer so I'm not crying about lost work, just annoyed that I can't troubleshoot this problem.