MD Walkman MZ-N420D I think.
I am using Sony discs that came with it and switched discs many a time and same results.
I am trying to put on songs that I've downloaded or copied from CD onto my hard drive... Any songs I put on the discs DIRECTLY from CD work great.
I have a few USB ports and have a webcam plugged into one which I unplug when I go to burn discs just in case...
So, yes, there is some software that also runs off the USB ports.
I hope that answers all the questions and maybe I can get some help.