You should be able to get PIP from any two video signals that are plugged into your TV. Let's say you run cable to it, even though you are using a cable box. Then your PIP choices would be any two of the following:
non-premium cable, tuned in by the TV cable tuned in by the cable box DVD on the component input LaserDisc on the S-video input surveillance camera on the standard video input.
And egg roll if you do it right the first time.
A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw