Re: AC @ 12:49 - Google vs Microsoft
The key was that IBM published the technical specifications of the IBM PC, just as they did for their larger, more expensive, products. That openness allowed other companies to supply add-in boards and peripherals that IBM did not supply, and when the BIOS was cloned, complete compatible systems could be produced.
As a *nix-based Brit, I do not know the exact details of MS's behaviour from personal experience, but the gist seemed to be 1. they promised system producers to undercut the prices of their OS competiors and 2. they would supply MSDOS even cheaper, if the manufacturers didn't offer a competing OS at all. This uncompetitive behaviour was eventually stopped, but too late for the competition.