Well with dell and others looking at ubuntu ( a free linunx desktop os) with the price of pcs now the oem os is a huge cost for those that buy them ready made.
In fact you can even get a free cd send to you in most countries in the world.
http://en.wikipedia.org/wiki/Ubuntu_..._distribution)
you can get a stripped down version which works as a webbroswer in vmware player called browser applicance http://www.vmware.com/vmtn/appliance...rowserapp.html
This gives you an idea of the program and real handy as you can run it on a normal windows xp machine.
There is a lot of opensource software which can be handy if you need to kit out a pc with software which works, is legal and does not cost the earth.
Openoffice is a good example, which does many of the things office does for no cost.
