SideTris is a fine Windows gadget that will let you play Tetris on your Desktop.
You can change color schemes, pause and resume a game, double the size of the game board, etc. The panel of SideTris will let you see your score and game status.
You can have SideTris gadget waiting for you right on your Desktop, to enjoy a Tetris break whenever you like.
Save the .gadget file to install later, or run it to start playing Tetris immediately