Usually power-on beeps indicate a problem with RAM or the RAM slots on the motherboard. However, there doesn't appear to be a 3 short, 1 long beep sequence indicated. Any chance you tried a firmware update recently that did not complete properly? If so check the accompanying documentation with the update to see if that beep sequence is related. Otherwise take the computer to an Apple service center for diagnosis or run the hardware diagnostics:
Insert the OS X installer disc that came with the computer into the optical drive and restart the computer. After chime press and hold down the 'D' key until the diagnostic screen appears. Run extended diagnostics.
Obviously, if the problem is failure of the POST tests, then the computer will not boot from the DVD.
