The stability of Windows 2000, the multimedia flash of Windows Millennium, and a new fee scale designed to keep Microsoft Corp.'s coffers full are expected highlights of Windows XP, the operating system being launched (but not released) today. Formerly code-named "Whistler", Windows XP is scheduled to ship by the fourth quarter and is expected to appeal mostly to consumers. It also consolidates today's Windows family: Windows XP is the successor to both Windows 2000 and Windows Millennium. It's expected to be more stable because it uses the same code base as Windows 2000 and NT, which target business users. But this version of Windows isn't for everyone. For one thing, you won't be able to jump from Windows 95. Beta versions of the software, at least, do not support direct upgrades from Windows 95; you must be running at least Windows 98. Microsoft says that is because most PCs still running Windows 95 simply won't meet Windows XP's processor and memory requirements. Even if you've already upgraded to Windows 98 or later, XP may be more hardware-hungry than your system can handle. Windows XP's CPU requirement will at least match and maybe exceed that of Windows 2000. And Microsoft is already recommending at least 128MB of RAM for Windows XP, compared to 64MB for Windows 2000. But one of the biggest changes is not technical. Windows XP also marks an attempt by Microsoft to sell its software on a subscription basis, a strategy it hopes will strengthen revenue down the road, according to Chris Le Tocq, an analyst at research firm Gartner Group. "When you purchase Windows XP you will buy it at a low [cost] but will have to agree to pay each year," Le Tocq says. "Our recommendation on the business side is that organizations not pay any more than 25 percent of the upgrade price. I am sure Microsoft will go over that, but the question is by how much." Microsoft hasn't said how it intends to implement the new scheme. However, the company is also exploring a subscription model in its plans for Web-based applications and its .Net strategy of Web-housed desktops. Le Tocq expects Windows XP will draw more attention from consumers than businesses, although Microsoft's official line is that the operating system is suitable for both audiences. Microsoft would not comment on Windows XP's pricing or features, or on Tuesday's event. But Windows XP is already in the hands of beta testers, who report that it provides many of Windows Millennium's multimedia features coupled with the better stability and security of Windows NT and 2000. "There will be a vastly improved user experience, particularly for the 9x users," says Rob Enderle, an analyst with Giga Information Group. "It is far more stable, reliable, and secure than the 9x base. Unlike Windows 95, this actually delivers on the promises." Along with the new interface, you'll find such Windows Millennium features as the Windows Media Player 7, Movie Maker, and the Home Networking wizard, as well as the System Restore function, which lets you roll back your PC's configuration to a previous state. It also includes management software that remembers log-in names and passwords for Web sites and servers, and some text-to-speech capabilities. The multimedia tools include applications to work with digital photos, enhanced music and video controls, and CD burning software, analyst Enderle says. Microsoft has said the software will make it easier to create, organize, and share images and other media files. Although Windows XP consolidates Microsoft's Windows line, the new operating system will be available in two editions: Personal and Professional. One distinguishing feature of the Professional edition is the ability to dial into your office PC and control it remotely. The Personal edition provides a modified version of that function; you can request help from a friend and let them dial in to take control of your machine, chat, or upload files. Microsoft has indicated Windows XP will allow mobile users to access their information on a variety of devices. Windows XP will also expand Microsoft's "connected home" concept with features that help devices in the home share multimedia content. Music files, for example, could be exchanged between a PC and an Internet-ready home stereo in another room. A second beta release of Windows XP is due this quarter, according to Microsoft representatives. Bill Gates, chair and chief software architect at Microsoft, will kick the event into high gear. He's expected to walk the crowd through the operating system's new features in what's likely to be a multimedia extravaganza. It has the right venue. The launch is taking place at the recently opened Experience Music Project, the $240 million museum and theatre built by Microsoft cofounder Paul Allen. In 1995, for the launch of its Windows 95 operating system, Microsoft's theme song was "Start Me Up" by The Rolling Stones. Rumour has it that Jimi Hendrix's "Are You Experienced" might be the accompaniment choice this time around. Allen built EMP as homage to Seattle native Hendrix. But analyst Enderle suggests the glitzy new operating system warrants a more contemporary tune. "Given the audience they are going after, I think Britney Spears might be the right choice," Enderle says. "This is a consumer release. They want to push the multimedia side. A lot of early adopters will be the aging Gen Xers, not the aging baby boomers." Enderle compares the Windows XP user interface to the Aqua interface in Apple's Mac OS X, which is due in March. Aqua has large rounded icons, myriad menu options, fluid control of applications, and a turquoise color scheme. Windows XP should also be more user-friendly, modern-looking, and showy than its predecessors, he says. "The capability is there to make it look like an Aqua clone," Enderle says. "This is going to be a very Apple-like launch." Microsoft is also working on handwriting recognition, as well as text-to-speech functions. But Enderle says they're unlikely to satisfy users just yet. "That is primarily because Star Trek set the standards too high," he says.