This web site lists three small portable Windows games for you to try out: http://stuff.goatdairying.com/programs/games/games.html.

Clicking – Just click on like-coloured heads of three or more vertical or horizontal groupings and do it quickly. This game is so simple but it’s extremely addictive.

Uno – The classic card game!

Logix – I didn’t play this one yet but it’s a little logic game.