emachine decktop model W2040?

The computer can not come on the monitor the green light led don't come on ,even I turn the power on.my little nephew was typing on the keyboard,Idon'tknow what he did .I thought it be from the temperure of my house being cold.I even place the pc.where warm air would blow into the motherboard,with the sidecover off.When the pc is on ,I could hear the hard drive spinning.when it first comes on i hear two noise one after another coming from the C D drive. Also ,i tryed another power supply.still the moniter has nothing in the screen. When,the pc is on ,i see the cooler fan spinding.I have the desktop,mainboard guide and the restore cd that came with the pc.The pc has window xp home edition.