need some pc help

[sfmarine]

A lady dropped off a computer for me to look at....I said sure. I connect the power supply and the computer turns on automatically??? odd I didn't even connect the screen yet so I had no idea what was going on. It made a few irregular beeps and then shut off. I took the computer apart and found the hard drive was not connected....I thought "problem solved" well now it won't even boot up at all. The computer has an odd smell coming from it but the motherboard light is on so that means the MB is ok right? I'm trying to figure this out. If anyone can shine some light...let me know! thanks