Yay! I’m typing this from my new motherboard and case. It seems to be stable this time around. However, the case outlet fan is very loud and I think I’ll end up replacing it and/or throttling it down.
Also, the CPU temperature is a little higher than it was before. When I first installed the CPU (an Athlon XP 2000+), the heatsink had this phase-change sludge on it and it was able to cool the chip to the low 40s degrees Celcius. I had to remove the phase-change stuff because it can only be used once, and I replaced it with some thermal conductive paste. Now the CPU runs at just over 50 degrees Celcius. I do notice that if the cover of the case is off, the CPU cools down by a few degrees, so there may be a slight airflow issue. I might replace the ribbon IDE cables with round ones so the air moves better.
Oh, BTW: if you are trying to hook up a case fan, DON’T confuse the black and yellow leads! I, uh, let the magic smoke out of one fan this afternoon.