its likely it needs a new power supply and motherboard. One thing that you can try is to unplug all cables from the machine and hold down the power button (on/off button) at the front of the tower for 30 seconds. Then plug just the power cable into the machine and see if it works. If fails, then you will most likely requrie a new power supply and motherboard as emachines have known issues on certain models
Kash, April 2006