A. Demand Substitutability

1. Server Operating Systems

19. Consumers could not turn from Intel-compatible PC operating systems to Intel- compatible server operating systems without incurring substantial costs, since the latter type of system is sold at a significantly higher price than the former. A consumer intent on acquiring a server operating system would also have to buy a computer of substantially greater power and price than an Intel-compatible PC, because server operating systems generally cannot function properly on PC hardware. The price of an Intel-compatible PC operating system accounts for only a very small percentage of the price of an Intel-compatible PC system. Thus, even a substantial increase in the price of an Intel-compatible PC operating system above the competitive level would result in only a trivial increase in the price of an Intel-compatible PC system. Very few consumers would purchase expensive servers in response to a trivial increase in the price of an Intel-compatible PC system. Furthermore, a consumer would not obtain a satisfactory substitute for an Intel-compatible PC operating system even if he purchased a server, since server operating systems lack the features -- and support for the breadth of applications -- that induce users to purchase Intel-compatible PC operating systems.

2. Non-Intel-Compatible PC Operating Systems

20. Since only Intel-compatible PC operating systems will work with Intel-compatible PCs, a consumer cannot opt for a non-Intel-compatible PC operating system without obtaining a non-Intel-compatible PC. Thus, for consumers who already own an Intel-compatible PC system, the cost of switching to a non-Intel compatible PC operating system includes the price of not only a new operating system, but also a new PC and new peripheral devices. It also includes the effort of learning to use the new system, the cost of acquiring a new set of compatible applications, and the work of replacing files and documents that were associated with the old applications. Very few consumers would incur these costs in response to the trivial increase in the price of an Intel-compatible PC system that would result from even a substantial increase in the price of an Intel-compatible PC operating system. For example, users of Intel-compatible PC operating systems would not switch in large numbers to the Mac OS in response to even a substantial, sustained increase in the price of an Intel-compatible PC operating system.

21. The response to a price increase would be somewhat greater among consumers buying their first PC system, because they would not have already invested time and money in an Intel-compatible PC system and a set of compatible applications. Apple does not license the Mac OS separately from its PC hardware, however, and the package of hardware and software comprising an Apple PC system is priced substantially higher than the average price of an Intel-compatible PC system. Furthermore, consumer demand for Apple PC systems suffers on account of the relative dearth of applications written to run on the Mac OS. It is unlikely, then, that a firm controlling the licensing of all Intel-compatible PC operating systems would lose so many new PC users to Apple as the result of a substantial, enduring price increase as to make the action unprofitable. It is therefore proper to define a relevant market that excludes the Mac OS. In any event, as Section III of these findings demonstrates, including the Mac OS in the relevant market would not alter the Court's conclusion as to the level of Microsoft's market power.

3. Information Appliances

22. No operating system designed for a hand-held computer, a "smart" wireless telephone, a television set-top box, or a game console is capable of performing as an adequate operating system for an Intel-compatible PC. Therefore, in order to adopt a substitute for the Intel-compatible PC operating system from the realm of "information appliances," a consumer must acquire one or more of these devices in lieu of an Intel-compatible PC system.

23. It is possible that, within the next few years, those consumers who otherwise would use an Intel-compatible PC system solely for storing addresses and schedules, for sending and receiving E-mail, for browsing the Web, and for playing video games might be able to choose a complementary set of information appliances over an Intel-compatible PC system without incurring substantial costs. To the extent this substitution occurs, though, it will be the result of innovation by the producers of information appliances, and it will occur even if Intel-compatible PC operating systems are priced at the same level that they would be in a competitive market. More importantly, while some consumers may decide to make do with one or more information appliances in place of an Intel-compatible PC system, the number of these consumers will, for the foreseeable future, remain small in comparison to the number of consumers deciding that they still need an Intel-compatible PC system. One reason for this is the fact that no single type of information appliance, nor even all types in the aggregate, provides all of the features that most consumers have come to rely on in their PC systems and in the applications that run on them. Thus, most of those who buy information appliances will do so in addition to, rather than instead of, buying an Intel-compatible PC system. Not surprisingly, then, sales of PC systems are not expected to suffer on account of the growing consumer interest in information appliances. It follows that, for the foreseeable future, a firm controlling the licensing of all Intel-compatible PC operating systems could set prices substantially above competitive levels without losing an unacceptable amount of business to information appliances.

4. Network Computers

24. A network computer system (sometimes called a "thin client") typically contains central processing components with basic capabilities, certain key peripheral devices (such as a monitor, a keyboard, and a mouse), an operating system, and a browser. The system contains no mass storage, however, and it processes little if any data locally. Instead, the system receives processed data and software as needed from a server across a network. A network computer system lacks the hardware resources to support an Intel-compatible PC operating system. It follows that software applications written to run on a specific Intel-compatible PC operating system will not run on a network computer. Network computers can run applications residing on a designated server, however. Moreover, a network computer system typically can run applications residing on other servers, so long as those applications are accessible through Web sites. The ability to run server-based applications is not exclusive to network computer systems, however. Generally speaking, any PC system equipped with a browser and an Internet connection is capable of accessing applications hosted through Web sites.

25. Since the network computing model relies heavily on the processing power and memory of servers, the requirements for the user's hardware (and thus the price of that hardware) are low relative to those of an Intel-compatible PC system. Still, a user who already owns a relatively expensive Intel-compatible PC system is not likely to abandon the investment and acquire less powerful hardware just because one of the least expensive components of his PC system -- the operating system -- is substantially more expensive than it would be under competitive conditions. Just as does the Mac OS, the network computing model presents a somewhat more attractive alternative to the first-time computer buyer. But as in the case where a prospective purchaser is considering acquiring the Apple alternative, a new buyer considering the network computing model must choose between types of computer systems. If the consumer opts for the less expensive hardware of the network computer, that hardware will not support an Intel-compatible PC operating system; and if the new buyer opts for the more expensive hardware of an Intel-compatible PC, an Intel-compatible PC operating system will almost certainly come pre-installed (and in any event represent very little additional cost relative to the price of the hardware).

26. Only a few firms currently market network computer systems, and the systems have yet to attract substantial consumer demand. In part, this is because PC systems, which can store and process data locally as well as communicate with a server, have decreased so much in price as to call into question the value proposition of buying a network computer system. This fact would not change if the price of an Intel-compatible PC operating system rose significantly, because the resulting change in the price of an Intel-compatible PC system would be very minor. Another reason for the limited demand for network computer systems is the fact that few consumers are in a position to turn from PC systems to network computer systems without making substantial sacrifices; for the network computing option exhibits significant shortcomings for current PC owners and first-time buyers alike. The problems of latency, congestion, asynchrony, and insecurity across a communications network, and contention for limited processing and memory resources at the remote server, can all result in a substantial derogation of computing performance. Moreover, the owner of a network computer is required to enter into long-term dependency upon the owner of a remote server in order to obtain functionality that would reside within his control if he owned a PC system. If network computing becomes a viable alternative to PC-based computing, it will be because innovation by the proponents of the network computing model overcomes these problems, and it will happen even if Intel-compatible PC operating systems are priced at competitive levels. In any case, that day has not arrived, nor does it appear imminent.

5. Server-Based Computing Generally

27. As the bandwidth available to the average user increases, "portal" Web sites, which aggregate Web content and provide services such as search engines, E-mail, and travel reservation systems, could begin to host full lines of the server-based, personal-productivity applications that have begun to appear in small numbers on the Web. If so, increasing numbers of computer users equipped with Web browsers and IAP connections could begin to conduct a significant portion of their computing through these portals. To the extent they might do so, users probably would not regard the Mac OS's limited stock of compatible applications as the major drawback to using an Apple PC system that it is today, and they might be increasingly drawn to network computer systems and information appliances. The variety and ease of use of server-based applications accessible through browsers would have to increase a great deal from today's levels, however, before the total costs of dispensing with an Intel-compatible PC operating system would decline sufficiently to impose a significant constraint on the pricing of those systems. Again, that day is not imminent; for at least the next few years, the overwhelming majority of consumers accessing server-based applications will do so using an Intel-compatible PC system and a browser.

6. Middleware

28. Operating systems are not the only software programs that expose APIs to application developers. The Netscape Web browser and Sun Microsystems, Inc.'s Java class libraries are examples of non-operating system software that do likewise. Such software is often called "middleware" because it relies on the interfaces provided by the underlying operating system while simultaneously exposing its own APIs to developers. Currently no middleware product exposes enough APIs to allow independent software vendors ("ISVs") profitably to write full-featured personal productivity applications that rely solely on those APIs.

29. Even if middleware deployed enough APIs to support full-featured applications, it would not function on a computer without an operating system to perform tasks such as managing hardware resources and controlling peripheral devices. But to the extent the array of applications relying solely on middleware comes to satisfy all of a user's needs, the user will not care whether there exists a large number of other applications that are directly compatible with the underlying operating system. Thus, the growth of middleware-based applications could lower the costs to users of choosing a non-Intel-compatible PC operating system like the Mac OS. It remains to be seen, though, whether there will ever be a sustained stream of full-featured applications written solely to middleware APIs. In any event, it would take several years for middlware and the applications it supports to evolve from the status quo to a point at which the cost to the average consumer of choosing a non-Intel compatible PC operating system over an Intel-compatible one falls so low as to constrain the pricing of the latter systems.