The family computer in my home experiences intermittent and comparatively frequent boot problems.

What happens is, the IBM ThinkCentre M52 (model 8113-D5U) will show a POST error (which I've never once bothered to write down, as I already know the basic cause). Re-attempting to boot and entering the BIOS reveals that the "Video" setting under "Devices" has been automatically set to "PEG". Changing it to "PCI" allows the machine to boot with a 90% rate of success (it occasionally shows only a black screen and does not load an OS or the BIOS), but the damn thing frequently resets itself to the non-functional "PEG" setting, re-triggering its boot problems.

(For those who are not aware, "PEG" is a term for "PCIe" whose existence seems entirely pointless. "I MAKE UP UNNEEDED JARGON ACRONYM, I ARE SMART NOW? ")

So my question is, why does this piece of crap keep resetting its BIOS to use a completely non-functional video setting? And how do I stop it from doing so?

BTW I ran CPU-Z, and all it can tell me about my graphics is the two GPUs are both called "Intel(R) 82945G Express Chipset Family".

EDIT: I should note: when the problems first started, the machine used "IGD" as the video setting. I changed that to "PCI" and now the video problem only manifests when the damn thing changes itself back to "PEG".

Maybe the battery is low?

But wouldn't a low/failing battery reset everything, including things like the system clock?

I'm not sure. Maybe some memory banks just get enough juice to keep their memories, while others start to fail.
Or it's your family interfering. Set a password.