From Grey Olltwit Software:
Place your bets and be the jockey or watch the race. To play the game above just follow the instructions on the titles screen and choose to either watch the race or be the jockey. To watch the race is just that i.e. to sit and see the horses battle it out over the furlongs and fences. To be the jockey of your chosen horse you control it by the Right Arrow Key for forwards and press the Ctrl (Control) key when you need to jump. If you don't jump in time your horse may refuse to jump the fence and stop dead. In this case you need to ride back a little using the Left Arrow Key, and then right arrow key to attempt the jump again.
Also on the titles screen, you can set how much you wish to bet on your chosen horse to win the race. This is called your stake and is set by the drop down box. Initially you are given 100 (Ã?Â£,$'s it's up to you) and each bet is deducted from this. The amount you win is determined by the odds of each horse, also shown before each race. For instance to bet 10 on a horse to win at 3/1 means if your horse wins you will receive 3 times the amount you bet i.e. 30 plus you get your bet of 10 back making 40 in total.