The MS information on that error points to a corrupted pool header. Look over the information on that at Bug Check 0x19: BAD_POOL_HEADER
That would explain why something is trying to load into a system protected memory address ending up with a BSOD typical of a corrupted device driver or even bad ram. But you already ruled any memory faults being seen with memtest suggesting some system files or volume information was lost somehow.
superdave1984 may have a good idea to look at there as well. See what the bios is set to as far as AHCI or sata/Raid modes are concerned. The problem on an older system especially if that is still the original factory install is that too many unknowns can be seen.
The hard drive itself may now be seeing bad sectors or some simple problem on the board like a weak battery could be the reason all types of odd errors are coming up. Still have the original battery on the board? Still running the original copy of Windows probably seeing a ton of invalid entries in the system registry? Those are things to look at as well in order to narrow things down even further.
How can I find out if that is the case?
No AHCI setting in the BIOS to look at... there are some like CAS, TRCD, TRP and TRAS which I am confused about though. As far as SATA/Raid... there is only one SATA device and I can't mess with how it is set-up, no RAID.
I've replaced the battery, the windows is SP3 that I bought at Fry's, so it isn't exactly a standard OEM windows version. In fact, nothing is OEM.
I haven't got the DRIVER_IRQL_NOT_LESS_OR_EQUAL since I got rid of fwcore.sys, but now I'm getting various POOL errors, whatever that is, whenever I play certain games or go to certain sites. I got BAD_POOL_CALLER not to long ago. What is a pool anyway? What does it do?
I think my best bet is a full reinstall of windows and a reformat of my HDD. Microsoft is being utterly unhelpful, none of their solutions work and they want money for me to even send them an email(crooks) asking to help. Those mindumps are the key to finding the problem but reading them seems to be impossible.
But I do have a question: In my BIOS, I have a settign for DRAM/FSB ratio. the options are AUTO, 1:1.00, 1:1.33 and 1:1.67. I have it set on Auto, and my timing is locked at 4-4-4-12. When I put it on 1:1.00(which is what I've heard is typically best) the timings are like 4-4-9-15 I think... should I have it on this setting or AUTO? Don't know if that's the problem, I think its a bad driver or something, just thought I'd ask.