On my laptop, I haven't booted into Windows for several months, and I am running out of free disk space, so I decided that I would delete my windows paritions and then resize my root partition. This page mentions the GParted Live-CD as an easy way to accomplish this.
Once I booted the CD, it was very easy to delete the partitions, and specify the size of the root partition. I was a litte worried about my situation, because my existing parition needed to be moved in addtion to being resized.
But it worked perfectly, and after a few hours, my parition is 70GB larger.