I find it disappointing that the previous reviewers to this game have not simply tried to relaunch the game a couple of times. This game DOES indeed work. The first time you launch it gives you a message that you must start the game from the launcher. You must wait a few seconds and click to start the game again. This will launch the game.
Sometimes you get the install page but just press exit and launch again. This process is so simple and takes a matter of seconds, and considering how great this game is when you play it, I'm surpised and ashamed that others have not tried this.
THE GAME:
As for the game itself it is a lot of fun. This game is actually more fun than a lot of racing games for the pc as you don't have to hold down an accelerator button, the gears just go as long as you have air. It also helps to play using the pc as you can kind of cheat when you're supposed to be pressing left and right to gain air (just hold down both buttons at the same time and it fills your air gauge instantly).
This game also has the replay factor as there are lots of gears to unlock and some secret tracks too.
The downsides to this game are that very occasionally a track just doesn't load, you get the loading page but nothing happens. The only thing to do is to exit the game by pressing Alt+F4 and re-launch.
Another downside which is completely fixable is if you have a multi-core processor the game might run slow especially the snow battle stage. To fix this simply open the task manager: press Ctrl+Alt+Del when you launch the game go to task manager, find sonic riders under the list of processes, right click on it and select "set affinity" then deselect all the CPUs except 0 or 1 then go back to the game.
I know the above sounds complicated but the game will run easily and once you've done this process a couple of times it's such a quick thing it won't spoil your enjoyment of the game! :)
Oh, and if anyone is wondering I am playing this game on windows vista, and it works!