Natalie,
I started couch to 5k 5 weeks ago, and being about 40 lbs overweight, I decided that I would start with weeks of walking before I began what I considered to be "exercising". I would walk my dog for about 30 minutes at a brisk pace and come home. That was my pre-training.
The first workout of my actual exercise was difficult, but I was able to make it through, but barely. I was looking at the list of workouts and thought "really? There's no way I can do this". I found it great that, though, each run got a little easier in a sequence. I would fear the next week's tougher-looking schedule, but then for me it became a challenge. I said to myself that if I couldn't do it, I'd walk it out, regress to the previous week's exercises, and then try again next week.
As far as my running goes, I started week 4 two weeks ago, and due to a wedding I had to travel to, I was unable to finish it. So when I came back last week, I started with week 3 day 3, then did week4 days 2 and 3 when I came back, basically repeating week 4 but starting easier on the first day.
My point is, I think that it's OK if we don't do it in sequence, but just make sure to continue to push yourself, and even though a workout is hard, when you progress in it, there's a sense of accomplishment. Don't worry about shedding the pounds or even plowing the schedule straight through. Try to be healthier, try to find your limit, and then keep going at that rate until you feel that you can go a little more -- then raise your limit. That's what I've been doing, and I find it helps.
Oh and one more thing, the iphone/iTouch app is awesome! listening to my own music really makes my workout bearable.
I've dropped about 7 pounds in the 5 weeks I've been doing it -- I have a long way to go, but my target is to be able to run a 5k in october with some co-workers of mine, and I really tihnk I can do it! GOOD LUCK!!!
Chris