Yes you can do it. You might not be able to do it as fast or for as long as they do in the videos, but the beauty about beachbody videos is you can keep improving as you use them.
I love P90X and Insanity because they are challenging and it makes me feel good to get up there and do as much as I can even at the weight I am.
I am currently doing Insanity right now with Shaun T. and my husband is doing P90X. It's true that they are geared towards those already in shape, but there is no reason that if you stretch properly and take it at your own pace that you couldn't do it too!
Plus, you are BOUND to be sore after doing it because you're going to be working muscles and body parts you probably haven't used in a very long time if ever. I like that sore though. It's like I earned it!