mitskits

Hi all, I recently got a mz-nh700 hoping to convert my old personal recordings (done with my older mz-r50 and even some with my mz-r2) to wav and store them on my PC. However, SS 4.3 tells me that it will not transfer them because they were "recorded on another computer" when obviously they were not! Is there a way to transfer my old recordings? I would be grateful for some help here. I have spent some time looking around the forum for an answer but I am afraid I got lost so apologies if this has been discussed elsewhere (just point me to where I should look please in that case). thanks a lot, Dimitri