If you're a walker wanting to get into running, I found a great program to get you there. It was in my March/April 2009 issue of Women's Running magazine.
This is a ten week program where you workout four days out of the week. Before beginning you should be able to walk briskly for 20 minutes. You should also always consult a physician before beginning an exercise program.
* Week One: 5-min warm-up, 4 x (5 min walk + 2 min run)
* Week Two, 5 min warm-up, 4 x (5 min walk + 3 min run)
* Week Three, 5 min warm-up, 3 x (5 min walk + 5 min run)
* Week Four, 5 min warm-up, 2x (5 min walk + 8 min run)
* Week Five, 5 min warm-up, 2 x (5 min walk + 10 min run)
* Week Six, 5 min warm-up, 2 x (5 min walk + 12 min run)
* Week Seven, 5 min warm-up, 2 (5 min walk + 14 min run)
* Week Eight, 5 min warm-up, 2 x (5 min walk + 16 min run)
* Week Nine, 5 min warm-up, 2 x (5 min walk + 18 min run)
* Week Ten, 5 min warm-up, 40 min run
Here you go. 4 x (5 min walk + 2 min run) means you walk for 5 minutes then you run for two minutes and repeat again 4 times. Each week try and do the workout four times, but be sure to take it slow and get plenty of rest. Good Luck!