Well, I found bodyrock about a year ago. And I wasn't a beginner. If you want an @$$ whooping, you could be like me and start with Lisa's HIITMAX (the original 16 week one). I did 1-3 of the videos, 2-3x's per week. Got in great shape really quick, but probably walked funny for over a week.
My other (safer and not so insane recommendation) is to start with any of the intermediate videos. Great cardio, use weights, and assume you know the basics of squats/lunges/push-ups/etc.