With the old version of OS 10.3, the CD drive on our G4 iMac recognized the CDs that were burnt with the CD drive. Now, with 10.4.1, the iMac does not recognize the CDs burnt with the iMac (it does recognize all CDs store bought though, for example, Turbo Tax and music CDs). The icon for the CD does not appear but if the same CD is taken to the PC, it is recognized. It doesn't matter if it is a data file or music file. It just spins and then spits it out. If you put in a store bought music CD, the play list appears so it isn't a setting options or that the CD isn't working. It does burn CDs but then doesn't recognize those either. Take it to the PC and it sees and plays the music. We recently upgraded to 10.4.1 and added extra memory. Thanks so much!