Continuous Beeps

I bought a computer that was put together by someone from scratch. I thought I was having modem problems, so I carefully took out the modem and replaced it (same modem). Now, when I turn on the power, I get a continuous beep. I checked the keyboard & even tried another keyboard, but same thing. I was told that it was not the power supply.

HELPPPPPPPPPP!!!!

Will appreciate any suggestions!!

Thanks