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Microsoft was found to have a monopoly over operating systems software for IBM-compatible personal computers. Microsoft was able to use its dominant position in the operating systems market to exclude other software developers and prevent computer makers from installing non-Microsoft browser software to run with Microsoft’s operating system software. Specifically, Microsoft illegally maintained its operating systems monopoly by including Internet Explorer, the Microsoft Internet browser, with every copy of its Windows operating system software sold to computer makers, and making it technically difficult not to use its browser or to use a non-Microsoft browser. Microsoft also granted free licenses or rebates to use its software, which discouraged other software developers from promoting a non-Microsoft browser or developing other software based on that browser. These actions hampered efforts by computer makers to use or promote competing browsers, and discouraged the development of add-on software that was compatible with non-Microsoft browsers. The court found that, although Microsoft did not tie up all ways of competing, its actions did prevent rivals from using the lowest-cost means of taking market share away from Microsoft. To settle the case, Microsoft agreed to end certain conduct that was preventing the development of competing browser software.

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