asus p5vd2-mx wont boot, just beeps

I built my pc from scratch and when i started up i got a long beep and two short beeps continuously and no video display

the specs are P4 3.0 ghz hyper threading
ASUS P5VD2-MX motherboard
1 gig of ram, A DATA
160 gb seagate sata hardrive

i read somewhere that i should try to clear the cmos, and i did so and it posted but did not read my sata hard drive, and it says CMOS CHECKSUM ERROR then when i restart the beeping starts again.

please help, i need this computer and don't know what to do