Free chess computer game I am a chess novice.

Can someone suggest a good, free chess computer game that I can use to start to learn chess by playing against the computer?  Maybe with some different difficult levels...
It depends on which operating system you are running.  If you are running a Linux OS, there are many, many options for you to choose from.  One of the more-popular options is glChess.



It has a few features that make it a good game to learn on:


highlighting possible moves when selecting a piece
ability to turn board numbering on/off
keeps a history of moves
has a mechanism that allows you to iterate through  the move history to see the development of the board.
allows configuration of computer players using several existing engines.


Once you get a little more advanced, a good one is XBoard.  While designed to run on Linux, there is also a Windows port called WinBoard.



While it might not look as pretty as other games, it has plenty of options:


Like glChess, can be interfaced with several engines.
Can play over the internet.
Has an interface for Chess via email.
Maintains your games in SAN notation.


While very feature-rich, XBoard is probably a good one to get once you have a few games under your belt.  

If you are on a Windows OS (Windows 7 or Vista) Chess Titans is good for starting-out, too.  While probably scoffed at by many on this forum, the advantages of Chess Titans are:


Several levels of play (1 through 10) of increasing difficulty.
If you have Windows 7 or Vista, you probably already have it installed.
Aesthetically-pleasing (if you care about that).