Internet navigation is important. If a single firm exercises too much control over Internet browsers, competition in e-commerce markets will suffer. Interoperability is important. The usefulness of software programs often depends on their ability to work with other software programs. As indicated by the record in the trial and extensive documentation elsewhere, Microsoft has used interoperability as a weapon against its competitors.
Applications are important.
People buy PCs to run applications, and these applications have to work with other applications. Happily for those who place themselves entirely in the hands of Microsoft, files can be easily shuffled between the dominant Windows applications and the company's Microsoft Office applications. Indeed, Microsoft Office is as much a source of monopoly power as is Windows. They present many of the same issues - OEM licensing, bundling, product integration, access to programming interfaces, etc. Remedies should be forward looking.