I created an MP3 CD-R using ISO 9960 format in NERO, and it worked fine in the AD-2500. Also, I created a WMA CD-R using ISO 9960 format in NERO and the AD-2500 does not recognize the files as WMA. It does recognize the files and their names, but it does not detect they are WMA. Are there any Apex AD-2500 or AD-2100 owners out there that have successfully played WMA files on their player. If so, please let me know what process you used to create the CD-R. I'm stumped. I also tried MusicMatch to no avail. I'm wondering if my unit is just defective.