At least I think it is a hardware problem. I can not see any pattern of circumstances that might be causing it. Maybe someone on here will recognize whats going on.
This is a ~ten year old win xp desktop which has performed without any issues for at least 6 or 7 years. That last issue was a malware infection, fixed by an OS reinstall. It has OEM drivers and hardware, except a newer hard drive, about 4 years old now.
What happens is that from time to time this computer just sort of locks up. Sometimes (rarely) once or twice a day, usually not for weeks at a time. Has been going on for several months. When it does, the windows and the system tray stop responding to the mouse or keyboard. The mouse and keyboard are OEM, PS2 type.
There is an odd circumstance, probably significant but I don't know what it means. If I have Process Explorer by Sysinternals running at the time of the lock up, it's window will still respond normally to the mouse and keyboard while the other windows will not.
Sometimes but not usually, after a restart check disk will run automatically, always on D: drive, the recovery partition. Check disk always reports that there are no bad sectors.
It doesn't matter how much load is created by Firefox or any other combination of softwares.
Overload can be created that will slow it down, but not lock it up. Also, sometimes it locks up while using very little resources.
Doesn't seem to matter which or how many website logins are active in tabs.
Doesn't seem to be a heat issue.
One more factor that may be important. I always have the C: drive running virtualized after updating Avast & Spyware Blaster. So any malware EXEs that may have landed there would be gone. Same for any other changes that may have been made.
Avast scans come back OK. Haven't done any other scans for a while, but there has been no indication of malware.
I'm pretty sure this isn't malware, so you can cut loose with any advice you please.
Thanks in advance for any suggestions.