Without the beep (and assuming that the system speaker is working correctly), it's not just that no signal is being provided to the monitor, the system is not booting at all.
My suspects, in order, would be RAM, Power Supply, Motherboard. I'd start by removing and reseating the RAM sticks. If you have two or more try each stick individually.
Resetting the jumper is a good starting point, your motherboard manual will indicate where it is located. Alternatively, you can pull the battery out and leave it out for a while to accomplish the same thing.