Linux has been hovering around 3% market share for years. It makes a good Live CD rescue disk if you can find one that will boot on your machine.
i think that because of Live CD/DVD versions of *nix that percentage will eventually start to climb if it hasn't yet. The more people get familiar with it the more will want to use it. The marketing of *nix hasn't been great, Microsoft has to be saluted for their work on that end.
The Live CD/DVD is something that Microsoft should probably make more readily available to their customers. It would come in handy because of the reasons you've stated. i've used live DVD Linux disks when i've screwed up something on my Linux configuration. It is a very handy tool to have.