If it is beeping, then the board itself (hardware) is alive, as is RouterBOOT (bootloader). To use Netinstall on a 532, you really need to get the serial console working. If you tried a cable and got nothing, then you either have the wrong cable, or are using the wrong settings. Try a straight-through serial cable instead of null-modem. If that doesn't work then make 100% sure that you are matching the BPS rate of the Routerboard (RouterBOOT defaults to 115200) and that you configure for the standard Data/Parity/Stop of 8/None/1. If nothing works, then verify that your computer's serial port ACTUALLY works by hooking it up to something else.