i orded my motherboard (gigabyte), cpu (p4 2.8 with ht), 1g ram (Dual channel), and a geforce fx 5500. after i put all the stuff together and turn the power on. fans turn on (cpu and viedo card) harddrive run, cd rom run. it just that nothing showing up on the screen and it keep beeping(short continous one) when i check the manual form the mother baord, that beeping is meaning power failure. oh, and my power supply is 300watts. T-T can someone tell me whathappen

Pull the HDD and CDRom from the Power and try again. If she powers up and you get the Bios screen, they you are drawing more power than the PSU can deliver.

On a side note, I do not build P4 systems with less than a true 400w PSU. Too many devices that can draw more than the minimum 300watts the MB is supposed to draw.

i even try it with my friends 500w but the same problem still exsist. btw, the board power by a 24 pin thou suppose to be.. but the manual said 20 pin will still be ok. all the power supply i tried are 20 pin, i also tried using the converter thing to make it into 24 pin but it still doesnt work thou. so would it be the mother board defects?

If you MB has a 24pin Power connector, I would get a PSU with a 24pin Power Plug. I know that people will use converters, but its not well documented what the extra 4 pins do and a converter is not the real thing. I would get that type of PSU before calling the MB defective.