A little history.
The the early days of the IBM-compatible PC market (remember when they were IBM-compatible, and no "Wintel"?) the PC applications market was quite split. The dominant players under MS-DOS were:
Word Processing: WordStar, WordPerfect, Professional Write, OfficeWriter
Spreadsheet: Lotus 1-2-3, Quattro Pro and SuperCalc
Presentations: Harvard Graphics
Database: dBase, FoxPro (pre-MS purchase), Alpha/three, Paradox
Programming Languages:Turbo C, Turbo Pascal
Microsoft was making money from the OS, but in the applications market, they were a third-string player. Word (the DOS version), MultiPlan (spreadsheet), and their language products were notoriously unsuccessful.
With Windows (does anyone remember the original versions with non-tiling windows?) Microsoft got a lead on application development, and certainly had the inside track on how to develop Windows apps. While we waited for Windows versions of our favorite DOS apps, we bought what was available and "good enough" (the MS apps) for Windows.
As corporate buyers, we like to standardize. At a certain point, we had deployed enough of the Microsoft products where it would be too painful to switch relative to any benefit. (Painful either from a deployment standpoint or a licensing standpoint).
Microsoft also made inroads though bundling software in Office. While not illegal, it certainly made it difficult for single products to make inroads. Lotus Freelance was a far superior presentation graphics program to the first version of PowerPoint. But people used PowerPoint because it was essentially "free." The next version of PowerPoint blatantly copied all the best features of Freelance.
On a more nasty level, bundling "features" into the operating system to kill competitors has been an ongoing practice. Witness the inclusion in Windows of Internet Explorer (hurting Netscape), Windows Media Player (hurting Real Networks and others), and MSN and MSN Messenger (hurting AOL).
Microsoft's history of noncompetitive practices in the Operating System market have been well founded. By penalizing hardware vendors who chose to sell operating systems or user interfaces other than Windows (OS/2, GEM Desktop, BeOs, and later, Linux), they locked consumers out of those options.
Unfortunately, any remedy is too little, too late. The serious potential rivals are long gone, and people have settled into what they have. In the server market there is a chance, in the desktop market, it's all over.
Oh, and Apple's problems are their own damn fault.
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...Trot and Cap'n Bill were free from anxiety and care. Button-Bright never worried about anything. The Scarecrow, not being able to sleep, looked out of the window and tried to count the stars.