Alright, I was handed off this computer to repair, and this is all the info I have.
My friend was moving her desktop computer. It WAS on. It got dropped while on. She says after she heard the HD clicking.
Now, when you try to power it, it "turns on" but the monitor doesn't turn on. I verified that the monitor is working by plugging it into my own computer. I reseated every connection. I unplugged every device unnecessary for booting to see if any were culprit and it wasn't booting up still. All the fans turn on, the hard drive whirrs, but the monitor isn't picking the PC up. I have spare parts and I tried, one at a time, a new HD, a new graphics card, etc, and none of them worked. I plugged the hard drive into my own PC and it seems to be working.
The only conclusion I can draw is that the CPU or mobo got broken on the impact, but I'm hoping that's not it as she doesn't have the funds to replace it right now and she needs it for working. Does anyone have any other ideas, or any way to check for sure which it is? I couldn't see any physical damage on them, but my eyes also aren't the best.