To the extent that computers, and with them operating systems, are purchased for want, I agree with most everyone who posted. Talk about your wants for an OS, they probably each represent some of the market.

There is a second element -- need.

Corporations would buy only what they need for computers if they could do so cheaper. When Windows achieved its success it was the cheaper option that ran on more hardware that is no longer the case.

Look at recent news for Thailand -- to basically remain in the market Microsoft reduced its price for Office by 87%, and still seems to have lost. When a desktop computer costs $200 far more people are going to resent paying $200-800 for Microsoft software. Microsoft prices have to come down. When that happens Linux has a whole new competitor.

Linux for the most part, is driven by far more modest margins than windows. It is lean and competative in the new emerging markets.

With satisfied need comes popularity and maybe more software writers. Certainly Linux is already getting more sources that twist it to what people want. If the projects are GPLed we'll all eventually see the new products.

my .02