It's a freeware. So, you can use it freely. Launch Pong 2001 and click the Play button. To launch the ball, press the space bar. The game ends when one of the two players reach 21 points.
Many settings are available.
Here you can set the name of the two players and change the keys they use to move their paddle. Be careful, the speed of the ball increase really fast. The color and size of the table can also be customized here. The last setting is about the size of the paddles. While playing, you can see a number in the bottom right corner of the main window.