Hi, there is no "copy protection" on WAV files. Are you sure they are not WMA files? Because WMA files can be copy-protected (also, Powertracks and BiaB can create WMA files).

Your problem might be connected to this:

"It's even happened to me recently when my computer at work was "upgraded" from Windows XP to Windows 7, and all the music I had on my computer had to be reauthorized or something."

I've never actually encountered this myself - but it sounds like something to do with whatever you use as a media player. WMA is a Windows media format - and it can have copy protection applied, unlike formats such as WAV and MP3 which don't have copy protection.

What license did you have to download in order to play your own music?