Only need one installation of Win500, as it will start a second instance of Win500 from the same Win500 program. You do need two cables and two sound cards. I am using the sound card in the computer and a Sabrent USB sound card. Works great for me. By the way I also have a TRX-200 and a Uniden 996XT and Pro2096 on the same computer. But I don't record the audio on the Pro2096.