No, not all G4s come with a burner but it sounds as though you have (I guess you have a DVD (or CD) on the top and a burner beneath). To test in OSX > Apple menu > About this Mac > More info > Devices and Volumes > Bus will show the name of the CD-ROM devices. In OS 9 > Finder > in Apple menu > Apple system profiler > in Devices and Volumes look at the details under Internal ATA devices. What about software? Do you have burning software such as Toast?