I didn't know it but there's a free clone called inkscape (here's the windows version) and it's pretty sweet. I never used Illustrator, and when I tried I failed (thought it would be more like old old Corel Draw versions). But from going to Help > Tutorials on this, I was able to turn pro in no time at all...
Whether you want to learn or you're interested in Illustrator it's worth checking out how good this app is.
Here's a review of the latest version.