Walking is better than running, jogging biking, everything. Why? Walking can be controlled more than the more vigerous workouts.
As far as walking off weight, it's by all means a very possible feat. I lost 32 pounds in a year (mind you, I was reluctant to do so, as I was very beefy and strong) by walking. I'd walk 2-4 miles every day, like you stated, and the weight sure enough disappeared.
Mind you, walking is half the challenge. Eating right is a must. No more junk food, fast food, pop, etc. 3 meals a day with all the water you can drink is your best bet. Eating fried chicken? Peel off the skin. Crab legs for Christmas? Toss out the butter. Also, no juice unless it's freshly squeeze. Look on the back of a juice container at the sugar content and you'll know why...
Remember! You're out to make your body look great, and make yourself feel great. Every so often, go ahead and go to your favorite place ot eat as a treat. Some ice cream perhaps. While doing so though, don't forget your goal.