Boot-up problem

[vanni1472]

My computer recently wont boot. What I have observed is after I press the power button the optical mouse and all the lights on the keyboard is blinking, no beeps, and no display on the monitor. I've checked the power supply for any loose connections but all are still in place. The power on lights and the HDD led is lit. When I press the power button for a few seconds, the system shuts down. What could the problem with ths?

P4XFCU motherboard

64mb ati video card

256mb ddr266 memory 40 gb HDD

Onboard sound