Yes, of course you can if you are in reasonably good health and in shape. Be sure to modify if you need to, and keep pushing play.
If you are completely out of shape or not in good health, check with your physician or physical therapist first to determine what your abilities are. If you have no health problems but think P90x might be too much, try Power 90 first. It's not a piece of cake by any stretch, will give you great results and is a more progressive program for beginners or someone that has not worked out in years than p90x.