You did the honorable thing!
But I always take it as a challenge and refuse to yield to a stupid machine!
A way to determine if the MOB is toast is look for popped Capacitors. Seen that a lot. They will look exploded and smell bad. IBM's used to do that.
Put a brand new Battery in.
I would have then tried re seating the Processor chip. Check for overheating.
Put in a blank hard drive and see if the BIOS would come up.
On the pre SATA days the hard drive jumpers made a difference, but I forget how now.