This thing drives me crazy, but before I give up and end up in a recycling center, I'll try to consult with more experienced members.

I tested the board after buying it on the fleamarket, it was functional, so I installed components, installed OS W98SE and WXP on two hard drives and for a while everything was OK. Then one morning after powered on the PC was left with a black screen, no boot or beep, just rotating fans on the CPU and in the case and HDD LED was permanently light on.Even after unplugging the components and leaving only the CPU and RAM, deleting the CMOS and restarting it, nothing changed, so I decided I was out of luck and the board went to silicon heaven.

I removed it from the case and, while trying to measure the power circuits, managed to short circuit the mosfet in the VRM (description here Possibility of FET replacement )
After replacing the mosfets, the board ran fine, booted the system, and I ran some tests to verify that the replacement did not affect stability and functionality (3DMark, SuperPi, Prime95). To my surprise, after shutting down the PC at the next launch, the same fault again - no boot, no beep, black screen.
I tried a different CPU (Celeron and P4), a different RAM (Micron, Adata), a different AGP (FX500, GF6600GT, even onboard), a different PSU (Fortron 400W, Seasonic 380W) - no change.

The diagnostic card shows either no code or 0 and 00 (which I don't think are diagnostic codes) depending on which PCI slot it is located in. The fan on the CPU is spinning. The LED HDD activity is permanently lit. The reset button doesn't work. It is necessary to switch off the PSU with a switch on it.

What is incomprehensible to me: if I leave the board for a day, two without the CMOS battery, and then turn it on, always booting with the beep for the first time, it can be entered into the BIOS and configured, after the restart the lottery begins - sometimes it boots again, sometimes it falls back into the state of the fault described above. I noticed a strange voltage monitoring behavior in setup - for Vbat (which is the voltage of the CMOS backup battery, am I wrong?) BIOS reports a 3.21V, although the battery is removed from the slot and I will not measure any voltage on the contacts of the slot. If I shorted the contacts with my finger, the reported voltage will fall below 1V. Another peculiarity is the permanently illuminating HDD LED, although no HDD is connected. The CMOS battery is new, fully charged with 3.3V.

Given the board's unreliability, I can't use it in any rig, but before I take it to a recycling center, has anyone encountered a similar problem or can't think of someone where the root of the problem might be and how to solve it? The board would be a suitable candidate for dual boot W98SE/WXP. I did get a similar one with VIA K8M890, but there the VGA card blocks one of the two PCI slots with the cooler and I can't use 2 sound cards (Audigy 2 for WXP and EAX, ALS300 for W98 and DOS).

Thank you for your time.