Rip, mix, burn -- but not with the initial version of Mac OS X. The next-generation Mac operating system, which will be released Saturday, will not support CD-rewritable, DVD or DVD-recording drives -- key elements of recent Apple marketing campaigns. And even if Apple delivers a Mac OS X version of iTunes digital music software, as is expected Saturday, music lovers will not be able to burn CDs using it, according to sources who have used the new operating system. Apple will try to incorporate such functions in later versions of the new OS. Sources have previously said the new OS will not permit DVD playback or recording, but its inability to record CDs was not clear until now. Mac OS X, the first major revision of the operating system since its introduction in 1984, will appear on store shelves Saturday for £99 inc. VAT. Apple doesn't plan on shipping Mac OS X on new computers until summer. Consumers who buy the new OS will get a free copy of Mac OS 9.1, which comes on a separate CD in the Mac OS X box. By using Mac OS 9.1, they will be able to run older Mac applications and burn CDs. But in order to do so, they will need to shut down a computer running Mac OS X and restart in Mac OS 9.1. Mac OS X does deliver broad support for hardware, including a wide range of USB and IEEE 1394 -- or FireWire -- storage devices, PCI graphics cards, digital cameras, and the most commonly used Epson and Hewlett-Packard color inkjet printers. But the biggest advantage may be standard features found on other mature operating systems such as Unix and Windows 2000: the ability to easily run multiple programs at the same time, improved use of memory, and greater crash resistance, among other items. Apple, which refused to comment on Mac OS X's features before its Wednesday press briefing, also is betting its Aqua graphical interface will entice consumers and professionals away from competing products with what Apple considers blander and less-functional choices. But several people familiar with Mac OS X complained they were forced to revert to Mac OS 9.1 too often, mainly because of limited support for applications and some hardware. "The interface is just astounding and makes Windows pale in comparison, but I got so frustrated with the limited software support, I booted to Mac OS 9.1 and left it there," said one Mac OS X user who asked not to be identified. Some Mac enthusiasts also may be perplexed by the lack of support for CD-RW, DVD and DVD-R drives -- also known as optical drives. Apple is expected to add that support sometime before Mac OS X appears on new computers in the summer, but the company refuses to comment on the issue. Several testers playing with Apple's iTunes said they were stunned to find Mac OS X simply does not recognise CD-RW drives as anything more than standard CD-ROM drives. Apple had indicated that a downloadable version of iTunes would add CD-RW capabilities, but one developer who asked not to be identified said, "The software hooks for the hardware simply are not there." The ringer is the Mac OS X box, which states the software does not support the three optical drives. The problem also affects other types of optical drives, such as DVD-RAM. Several people who have the final version also complained they had trouble getting Apple's so-called Classic mode to work right with some older software. Apple's answer for supporting older software is basically running Mac OS 9.1 within Mac OS X. People who do not have Mac OS 9.1 already on their system have to install it from a separate CD before upgrading to Mac OS X. When booting the system, the person can choose to go to either Mac OS 9.1 or X. Under Mac OS X, Classic mode brings up Mac OS 9.1 within the newer operating system to run older software. But any software that must access hardware, such as Apple's recently released Final Cut Pro 2 and some other video-editing programs, apparently has problems. Classic mode, testers say, does not fully support internal or external hardware. The only way to use Final Cut Pro 2 and other hardware-dependent software is to reboot back to Mac OS 9.1, say those familiar with Mac OS X. The same is true for burning music or video discs or watching DVD movies. Classic mode's other shortcoming is that it does not benefit from some of Mac OS X's most coveted features, such as greater crash resistance and memory protection. Aside from the internal optical drives, overall hardware support is broad. Many USB and FireWire devices work right out of the box, including a wide range of USB digital speakers; digital cameras, including Casio's QV8000 SX and Kodak DC220, 260, 265 and 290 models; and LaCie and VST external hard drives, including some RAID models. Mac OS X also supports a wide range of add-in PCI cards. These include Adaptec 2930, 2940 and 3940 SCSI cards and most major video cards. On the notebook front, most removable storage devices used in older PowerBooks will work fine under Mac OS X. Another important change is simplified printer support. Older versions of Mac OS made hooking up network printers via AppleTalk fairly straightforward. USB and other non-network printers proved more troublesome. Mac OS X, however, provides basic inkjet printer support. Simply plug the printers in and they work. Supported printers include Epson Stylus Color 740, 760, 900 and 980 and many HP models, such as the 990C. Apple made a number of subtle changes to Aqua in response to customer feedback from last September's Mac OS X public preview. Many of the biggest differences are actually subtle. The Dock -- Apple's repository for documents, folders and some applications -- has taken on features from the older Mac operating system's Control Strip module. A battery-level monitor and display control, for example, have been added to the Dock, which offers display access in a pop-up menu. For Windows converts, one of the old operating system's most perplexing features has been dragging disk icons to the trash to eject floppies. In a subtle but significant tweak, when a disk icon is dragged to the trash, it now turns into the eject symbol found on newer Apple keyboards. Also in response to tester feedback, aliases to hard, optical and other drives appear on the Aqua desktop by default. Another adjustment is an Apple menu similar to that found on older Mac OS versions. From the menu, people can access features such as system level setting, sleep and start, and recently used applications and documents. "This feels more like previous Mac OS versions," said one person running the final version. "It left me feeling really good about Mac OS X." But she also noted that "it is a little jarring switching between Mac OS X and Mac OS 9.1. The change from one interface to another is really disconcerting." Another nice touch is the addition of column views to Apple's more traditional icon view of a folder's contents. This feature, which bears some resemblance to Windows, makes photos, Apple QuickTime movies and MPEG video appear in a preview pane from which the multimedia content can be accessed. QuickTime 5.0 will make its debut as part of Mac OS X. In yet another Windows throwback, Mac OS X fully supports pulling up menus with a right click on a multiple-button mouse. Testers also found that Apple's minimum 128MB of memory requirement was only required when using Classic programs. Running Mac OS X alone worked fairly well even with as little as 64MB of RAM. Have your say instantly, and see what others have said. Click on the TalkBack button and go to the ZDNet news forum. Let the editors know what you think in the Mailroom. And read other letters.