DVD - ROM plays DVD - won't read CD

[RRHODY]

I have a Toshiba SD-C2102 in a 600X (W2KPro) that will "read" DVD's fine, but many times, but not always, when a data CD in inserted a messages says disk not formated" (and the disk is commercially produced). I swapped the drive with a Toshiba SD-C2612 and got the same result. The drives appear in Device Manager as working properly. I assume there's something in Windows and the settings dear Bill has provided.
BTW, the DVD movies play in PowerDVD and WinDVD.