my pc is dead…please help!!!

My Pc will not boot although when turned on the power indicator lights up. My kids were using it and they said they say a blue screen before it shutdown. The monitor says it, the monitor that is, is working correctly and to check the cables and power, which i did. I created a boot disk by downloading from the net, but I don’t know if it’ll work. Also the indicator lights do not as it used to will the cpu was starting up.Please, please, please….help!!!