Where do you get a free chess engine that you could make all the moves for both sides and it gives scores based on how good a move is? 

http://www.cruxis.com/chess/houdini.htm here you can download houdini 1.5

http://www.playwitharena.com/?Download here you can download a good GUI to use the engine in

Just use Google.  Google is your friend.

Google "free chess engine" or something similar.  You should then find links to Houdini's homepage, Stockfish's home page, links to the Rybka, Komodo, and Critter engine, etc., etc., etc.

Check out the current rating list for a list of the top 242 engines:  http://www.computerchess.org.uk/ccrl/4040/

And yes, after downloading the engine, as Jabba mentioned you will then need a GUI (Graphical User Interface) for it.  My favorite is WinBoard, but Scid, Scid vs Pc, ChessDB, Tarrasch, ChessPad, ChessX, Fritz, Arena, and several others will all work too.