MiniRacingOnline is a free multiplayer racing game that allows you to test your skills against players from all over the world.
Graphically MiniRacingOnline is, well, a little basic; it looks like the old top-down console racing games of years gone by. This helps it to run on even the oldest PCs, though (even Windows 95 systems, at least in theory), and there's plenty of detail elsewhere to explore. You can take part in multiple competitions - F1, Karting, NASCAR, Rallying and so on - each with their own courses, then design your own tracks, customise your vehicle, and extend the program's playability with a host of add-on extras.
That's the theory, anyway. In practice we found the program to be a little confusing, failing unexpectedly at odd moments. On later investigation it turned out we hadn't done something correctly, but it might be more helpful if MiniRacingOnline had told us that, rather than simply closing down without comment.
In addition, place note that the program loads initially in Spanish: if that doesn't work for you, click the "Opciones" button and select your preferred language there. Then take a look around at the other settings on offer; it really is a very configurable game.