sometimes, i dunno for waht reasons, mobo doesnt have this beeps. anyway, try to chk first ur mobo speaker maybe its not connected.
ok first things first, you must disconnect first all you computer peripherals, like the IDE cables, the floopy and just put ur video card and of course the memory.
try to find what causes the problem by changing (if you have a spare) ur video card, your memory, the pwer supply and last thing to chk is your mobo.