okay so i opened my pc and actually dusted it, i didnt remove anything except for the ram so after coupling it back it just stopped working the fan and the light at the front but the at light at the back of the cpu is on and the optical mouse light also on
Go back over every connection from the power supply and case to the motherboard. Make sure everything is connected (correctly). Make sure you put the RAM back in all the way, you have to put some pressure on it.
You probably just disconnected a wire(s) and reconnected them incorrectly, or knocked them out unintentionally.