Hello Vogons members!

Longtime lurker, first time poster. I had hoped my first topic would be something a little more helpful to the community, but I'm having an issue with a PI-XP55T2P4 (S)S7 motherboard that I just picked up for a build. I wanted to list a detailed expanation of the process I've taken to troubleshoot my issue, but I've been battling with this board for three nights now, and I honestly can't remember everything that I tried. Here's a short explanation of the problem, and a list (in no particular order) of the solutions I've already tried. Hopefully someone can give me a good idea for what to try next.

The problem: Bought the board with 4 SIMMs of RAM, and a k6-2+ installed. The seller assures me the board functioned 100% before I received it. Has pictures of RAM and CPU tests, for whatever that is worth. I'm going to give him the benefit of the doubt, at least for now. Hooked the board up to a P4 era ATX power supply, which supplies -5V, and has something along the lines of 28A on the +3.3V and 30A on the +5V. Should be plenty of juice for a Socket 7 MB. Depending on how long the MB sat connected to the PS before I switched it on, I could get anywhere from .5 seconds of fan movement before it shut off, all the way up to the RAM test portion of the POST process, before it would shutdown. I've tried removing sticks of RAM, switching them with different sticks, and removing the TAG Cache chip on the MB. With only two sticks of RAM, the MB seems to power on longer. It doesn't matter what bank pair I use. I've taken out the BIOS chip and checked it on a EEPROM burner... and even re-burned the BIOS onto the chip. It had the proper patched BIOS to start with, and I re-burned the proper BIOS. Fresh CMOS battery. I've swapped out the K6 for a Pentium 200 MMX, and the MB will actually boot all the way to the "HD NOT FOUND" message... sometimes. If I let the board sit on the PS for a bit before startup, it will *sometimes* (meaning twice so far) actually boot up all the way. The more I power cycle, the shorter in the POST process I get before the MB will shutdown. With the K6, I would never get passed the memory test. The two times I've actually gotten it to boot, it seemed stable. The first time I let it run for about a minute, more so because I was in shock that it actually worked. The second, about 30 seconds. There has been nothing other than a Cirrus Logic PCI video card installed in the MB. Not even a keyboard. I've tested the video card and power supply on a DFI K6BV3+, and it will sit at the "HD failure message" for 15 minutes + without a hiccup. Am I looking at possible cap issues? Something with the voltage regulator? I find it odd that a p2 MMX (2.8v core) would get further into POST than a K6 2+ (2.0v core), but maybe I'm not looking at this the right way. Any insight or suggestions would be greatly appreciated. I'd really like to get to some benchmarking projects for Vogons!