screen capping programs

I've spent hours reading through every tutorial I can find on taking screen caps from DVDs and I've tried every last suggestion, even downloading programs like HyperSnap. I have tried WinDVD, Widows Media Player, and Realplayer and cannot get screen caps. No matter what controls I change on WMP for instance, trying to edit in PS7 the rest of the cap will move but the movie image will only stay in the same location as in the player and the cap will still only save as a black screen.

There has to be something that will work and won't cost me money I don't have. Thanks in advance for any help!