I want to preinstall my game Balls 2004
(http://mailsendplus.com/software_balls.htm) on to new computers.
Where can I find companies that allow me to do it?

You need to approach the computer manufacturers.  It might be worth
asking some questions about who their customers are to check that they
are the people who you're targeting your game at.  Small local shops
who sell refurbished systems and the like may be easier to persuade
than larger manufacturers.

Start with selling your game on ebay and Download.com