First off....

This is a wonderful place to be and very motivationg and inspiring.
Now, on to the question at hand..... I recently started working out again after a long (ok, very long) hiatus. I spent too many hours on the events boards and was inspired to start running and complete to WDW 1/2 next January. You can see from my siggy that I am not a small person. To be honest with you, even when I was in shape, I was not a runner. However, I started small. People on these boards suggested jogging for 30 seconds and then walking for 4 minutes and alternate like this for 30 minutes. (Don't forget a warm-up and cool-down.) I know it doesn't sound like much, but at first those 30 seconds about did me in. Now, I am currently up to jogging for 1 minute and walking for 3. Again, it doesn't sound like much, but for me, it is huge. I have not had to stop because of injuries or anything like that, and I just know I would have had to if I had done anything more strenous. As my pace increased, I had increased my distance as well. Starting this week, I am going to increase this to 40 minutes. I will also soon increase my jog time as well since jogging for a full minute has gotten pretty easy.
Anyway, that is what I'm doing, and so far, so good. I can see results in my stamina. I am losing weight -- slowly, but surely, and I know I'm losing inches. (This morning I wore a skirt to church I would not have been comfortable wearing just a couple of months ago.) I have been sore but have not suffered injury (shin splints, heel spurs, etc.). I also mix up the wogging with my elliptical machine and workout videos/DVDs.
Good luck to you. You can do it.