Chess Engine

Houdini 1.5, Stockfish and Firebird are all free; from what almost everyone around here says Houdini 1.5 is the strongest free engine in the world right now but getting the other 2 wouldn't hurt either.

You will also need a chess GUI to run any of these engines. Arena and Winboard are both free.

http://houdinichess.com/

Posting your question under "books & equipment" may have been a tad more appropriate, but I wouldn't lose any sleep over having posted it here.

http://www.rybkachess.com/index.php?auswahl=Demo+version

http://www.chess.com/download/view/houdini15

Also pick up Stockfish and Critter.  Both of these engines are also strong, and also free.  Also, the free version of Rybka, 2.3.2a, I think, is also worth having. 

(Finally, although it is no longer as strong as some of the others, no engine collection would be complete without Crafty.  Crafty was THE engine, for many years.)

In addition to WinBoard, which I recommend, and Arena (which I don't like myself) give Scid vs. PC a try as your GUI (graphical user interface) for the engine.  See my another post in this forum that mentions this program and gives a few screenshots.

Welcome to the wonderful world of chess engines.  Eventually, when you really get into it, you will be condcuting your own engine vs engine tournaments, downloading endgame tablebases, opening books, testing engines with different test suites, etc., etc., etc. 

MrEdCollins why do you recommend Crafty? I think I have it with F12 but have never used it (yet)...time is NOT on my side these daze!

I recently came across a position and Crafty solved it faster than all of my other engines, including Stockfish, Houdini, etc.

It has a long and detailed history.  It is written by Dr. Bob Hyatt, who is still very active in many different computer forums.  A lot of my old chess computer books mention Hyatt.  He wrote on or more of the chapters in one of my books on chess computers.

It was one of the first engines to support the use of multi processors, and pioneered the use of the bitboard data structure to represent the chess board.

It is free and open source.

It has features no other engine has.  For example it has an annotate command line feature.  And annotateh will produce an html file which includes a bitmapped graphical board for every position where Crafty makes a comment.

No engine today would be as strong as it is now, if Crafty had not been around.  It isn't the strongest engine any longer, but it was one of the first and has been around for what seems like forever.  I think the latest version is 23.4.  I think it's a cool engine to have, if you collect chess engines.

MrEdCollins.. great comments that give a lot of info and background. i am becoming an engone collector myself it seems. glad to see this is a disease others know of as well

THANKS for the info MrEdCollins I will check Crafty out, although I'm not sure if all of its features will be available in Fritz - but there's one sure way to find out of course.