I've replaced the system with an old one who used to be my personal system (cuz I replaced that one with a brand spaking new one
) but I did keep the mobo and CPU and would love to find a use for them.
Further testing actually got the fans spinning but it still wouldn't post or show any HDD activity (and I don't even know why it resumed spinning the fans as I had not replaced any parts or removed any parts).
My guess is one of the Voltage rails on the mobo fried. The question now would be if the CPU fried as well because it was left running or if power was never sent to it. I'd need to buy a new mobo to test out the theory properly though and that might be more trouble than its worth since a mobo of that era is a technological dead end now.