I re-started the regular Power 90 (not P90x) workout a couple days ago. It seems that the P90X is for people who are already used to aerobic activity. The Power 90 however, (I suppose it's a precursor for P90X), seems to start out simpler and less intense than the P90X series. For me, it's the perfect place to start because the first phase, allows you to do things a bit slower with some easier activities (although I have to get used to some of them to do them).

After doing it a couple days, i'm sore and am hopefull that I get some good results.

So if you are just getting into excercising, you may want to start with Power 90 first.