Net Gin Rummy - description from Softdepia.com:
Net Gin Rummy lets you play Simple, Standard or Oklahoma variations of this popular card game. You can play against the built-in computer opponent or/and against a human opponent through the Internet or a LAN. Net Gin Rummy provides you with two game table tabs that easy to change: you will be able even to play against the computer and human opponent at the same time! Each tab lets you select a game variations; change the scoring and rules of the game; customize cards, decks and backgrounds; choose text messages fonts and colors; define card speed; associate sound effects... To know more about this game you can read Gin Rummy rules on this page. Net Gin Rummy is fully compatible with Windows XP and can support themes.
Net Gin Rummy is a "Free to try" program. You can download and try it for an evaluation period.