How does one become a runner???

I've got an entry in the works for tonight with pictures of my food eaten, etc... but I've been sitting here thinking. How does one become a runner? I'm 230 pounds and overweight. I have flat feet and bad knees and back issues. I know that losing weight will help all of this... Ever since I was young, I've wished I could be a runner. I've never been in shape enough to run. Even when I was at my thinnest (135ish), I wasn't fit enough to run a mile. I forced myself to try my hardest to run a mile when I was this thin and I still failed hitting one mile in 13.5 minutes. That's a pretty long time for one mile, and I thought I was going to die/puke when I was done... and I also had terrible shin splints and my knees and ankles hurt terribly...

I would eventually like to try the Couch to 5K program, but as I'm not even in shape enough to walk one mile (I average between a 17-20 minute mile walk right now) I doubt I could even attempt that program yet. Any ideas how someone as out of shape as I am can become a runner? Give me some ideas!