I am probably missing something myself as I don’t know exactly what you mean by deleting files from the recorded list, or dedicated folder, but read on for my thoughts.
My reply is going to be of no comfort to you as I have no clue whether you can recover your files, but for prosperity’s sake I have to state:
I also had to ‘retire’ a pc unit just over a year ago and subsequently had to repurchase new versions of my NCH software when I got my current windows 7.
Fortunately all the countless hours of recording I had done previously were still available to me, and I don’t know why you would have a different experience...
I always save my files (read: set destination folder) - whether a recording via GoldenRecords, SoundTap, WavePad, etc.- to a folder and file format of my choosing (always .wav for my usage.)
Don’t rely on the defaults; always save in a folder and a format of your choice. How that could 'disappear' is beyond me.