At long last, Apple and Dantz Development have released the necessary software for Dantz’s Retrospect 4.3 (all versions, including Retrospect Express) to be able to back up to most of the CD-RW drives included in Apple’s iMacs, iBooks, and Power Mac G4s back in January of 2001 (see "Retrospect and Retrospect Express 4.3 Released" in TidBITS 541). The problem turned out to be surprisingly complex, in part because these were the first ATAPI CD-RW drives Apple has shipped and thus required new drivers, but mostly because Apple’s Disc Burner software assumes that it has exclusive access to the CD-RW drive at all times, preventing other programs from using it. The solution was the Shared Device Access Protocol, developed by Apple, Dantz, and Roxio (makers of the Toast CD burning software), and implemented in Apple’s SDAP Authoring Support extension, which enables SDAP-compliant control of Apple hardware starting with Mac OS 9.2.1 (see "Mac OS 9.2.1. Released" in TidBITS 594).
So, to use Retrospect 4.3 with supported internal CD-RW drives (including the Sony CRX140E and Matshita CW-7586 in the Power Mac G4, the Sony CRX700E and Toshiba SD-R2002 in the iBook, and the Matshita CW-7121 in the iMac; check Apple System Profiler to see which CD-RW drive you have), you need Mac OS 9.2.1, Retrospect Backup 4.3, Retrospect Driver Update 2.2, and Retrospect Extensions Updater (the latter two are free 650K and 150K downloads respectively; the Retrospect Driver Update 2.2 download requires your registration number). Dantz expects to announce support soon for the SuperDrive (DVD-R/CD-RW) and the CD-RW drives that shipped in the Macs announced at Macworld Expo NY in July of 2001 (see "Apple Speeds Up iMacs and Power Mac G4s" in TidBITS 589).