The first question to ask here is how much time and money you are willing to sink into this computer.
Generally, banging on it doesn't fall in my repair algorithm :D
That said, you have probably loosened a couple connectors inside from the banging. With the persistent overheating issue I also wouldn't rule out a connector creep, which is where the frequent heating and cooling (and therefore expansion and condensing) of internal parts may have loosened connectors.
The mouse more than likely caused a brief short if it immediately crashed the system without a BSOD. An IRQ/resource error is possible, but impossible to diagnose without being able to boot.
The symptoms you are describing currently indicates a problem at the motherboard level. The "peep" from the hard drive is indicative that the system is receiving power, however when the system fails to start the hard drive simply goes into a standby state because nothing is requesting any data from it.
The cap/num lock lights can also function as a POST error indicator if you notice it is flashing repeatedly.
So to give you an idea what is happening... There's probably some loose connectors inside, if not broken components. System board damage from excessive heat is a definite possibility. You are looking at several hours if you attempt to pull it apart yourself, and bill > value if you take it to the repair shop.
My advice? Remove the hard drive. You still have (hopefully) recoverable data and a "no operating system found" error would be a blessing at this point. The rest of the computer - circular filing cabinet #13
Edited by MDTechService, 02 January 2013 - 05:40 AM.