This is post is being updated at the end to reflect testing, still no solution found.
1/2 Full product name : Abit NF7-S 2.0, 2x TwinMOS 256 DDR400, AXP2400, ActionTec/I-tec ISDN PCI card, Leadtek GF3Ti200 TDH/64, HDDS: WD800JB (Prim/Ma), TEAC CD540 CDRW (Sec/Ma), Barracuda4/40GB (Sec/Sl), Seagate U6/60 (SiL SATA). PS/2 Mouse and KB. No USB devices.
BIOS 1.1, then 1.4) CPU/MB o/c to 190/280, 166/333 - tested.
3 WD800JB (as it was causing trouble) - 17.07.W17
4 2.03, Microsoft ones, graphics - 43.51
5 WinXP Pro SP1
6 Bug: STOP errors, with WD800JB spin off. most of times it was BAD_POOL_CALLER but not always. It developed after replacing Maxtor drive with WD one and clean reinstall of system. It was happening thru some weeks, typically once a day. It happened very randomly. Sometimes when computer was working heavy and sometime when just browsing inet, left for a few moments, coming back - bsod. The only common thing I can mention was Netscape Navigator and Winamp, during browsing the net.
I had switched on "CPU Interface" in BIOS, now works ok, but I am using other combination of software. Maybe it's just sleeping :-\. Now system is oced to 183/386. RAM = turbo 2-2-2-6. voltages - default.
PS. Before reinstall I had a bit atrange trouble with The All Seeing Eye, game server seeking software. I was getting STOP errors when updating data from net, but that time WinXP config was messed. It went thru some very different hardware configs without clean install, so I've blamed that thing that time. However no drive spinned off.
Edit: No change this bug is still active

, Switching off all o/cing
Edit2: Not helped, still the same, now trying 2942 audio drivers.
Observation: To me it looks like kind of stall of internal bus, it happens in moment of high disk activity (uncompresing, copying). It is precisely this way: Computer freezes for a second, then screen gooes black for another second, then disk shuts down and WinXp displays STOP error screen. Very often "system is unable to identify driver causing trouble". I have second config of win98 for developing some older software and gaming - error doesn't happens there (no single time), I can work and game all day without problems.
Edit3: 2942 - no help, trying 2.42 (w/o their audio). Not helped. Trying some different BIOS settings.
Observation: It looks like HDD cache is flushed before generationg STOP error, even if it hapens while copying I have seen any lost clusters and file sizes seems proper (when copying was stopped in mid, I have half of file) and delay between freeze is longer when there is lot of data to flush. I don't get it, if Windows is capable to flush disk cache from RAM, why it is generating these damn STOPs?
Edit4: I have checked all BIOS options could have impact on this issue. None helped.

:(:(. I think now it's WinXP/XPdrivers problem, cause on second partition Win98 works without any problems.
Edit5: As I don't use onboard LAN, FireWire and USB I've disabled them in BIOS. I thought that problems are generated by some resource conflict. To my suprise it got much worse, after connecting to inet I could browse for a few minutes max . to get this annoying error

(prev. it was after few hours always).
Edit6: Ok now after setting 'IDE Prefetch' option in BIOS to Disabled problems seems gone, altought I will do further testing.