Related to points 2 and 3, Microsoft didn't just make it easier to get the Windows tools, they made a tool that made it easy to write Windows programs: Visual Basic. Everyone loves to hate VB, but it was a huge factor in enabling line of business developers -- people who just need to bash out CRUD apps as quickly as possible, people who don't need the fine control of C/C++, people who want to knock together a bunch of forms rather than mastering the vast Windows or Presentation Manager APIs -- to create applications on Windows. And of course VB was also adopted by hobbyists and people creating simple utility programs, again ensuring that those programs would be available on Windows but not OS/2.