Boot

first thing to do is crack her open and unplug everything including the PCI cards and clear the CMOS via a jumper on the board then try to boot if that doesn work try taking the memory out , if it beeps then its more than likely memory, but if it still wont beep you either have a bad mainboard, powersupply or processor.

Let us know :-)

Then you more than likely have a bad mobo or processor. :-(

Do any lights turn on when you power it on? Can you here the fans spinning and hard disk working?