I solved the issue of the size of the box by dremmeling a slot on each side, approximately 6-7mm from the bottom. I removed the motherboard from the old case and slid it in to check the sides, and the slot works great.
So I reassembled the computer, hit the power button, and no POST.
Not even a POST beep. Mmmmm...
The fans all spin up (
PSU fan included), as does the drive, but the HDD activity LED did nothing. No signal to the monitor, either.
I pop out the wifi pci card, the vid card, the
RAM, reattach them all, nothing.
Remove the vid card, and try the on-board video, nothing.
So maybe it's the
PSU. I swap it out for the above-mentioned mini 150W, turn it on...
SMOKE!!! SMOKE!!
So much for that
PSU.

It went bye-bye. Not sure if any more damage was done to the board/
CPU.
So if I decide to continue this mod, I have to either figure out what I did to the motherboard or get a new one. I probably zapped something with static, or simply reconnected something incorrectly.
I also need to order a new
PSU. Perhaps a Sparkle Power 200W.