I'm looking for a software (engine) that would tell me after each move which side has a winning, losing or equal position. I know Fritz does that, but are there any free engines doing it?

You can use the Crafty or Toga engines with Scid to do analysis. Scid also has an "Annotate" feature that will automatically add possible variations to a game or set of games.  It will also score positions.

I second Sajchurchey's recommendation. (I like ChessDB better than SCID... ChessDB is built from SCID, the two look nearly identical. Both are excellent.)

BTW, all the "engines" do this ... what you need is an engine + engine interface (the GUI).  ChessDB is a free database program that has a simple engine interface for analysis. (If you want to play against the computer you'll want Fritz or Chessmaster) Get "Stockfish" as a free engine to use in ChessDB. It's strong fast and stable, I like it even better than Toga II (which I used to use).

Yes, thanks both of you for the info. I knew about the rating thing but it slipped out of my mind when I saw fritz's graphs. I'll also take a look at ChessDB to see what it has to propose

Rybka 2 is free now, and still stronger than Fritz. Run it in Winboard or similar.