Problem with checklists help needed

Hi All. I have a problem when I try to select the preflight checklist the yellow light comes on but no sound. I have assigned keyboard controls and tried my joystick for the master button. Still no luck. I uninstalled the progam and re installed it loads of times also i have reinstalled direct 9 but still no luck. Im using windows XP with fsx. What ever checklist I select none of them work i have been trying for a few days and now im wondering if i have wasted my money. Would appreciate some help please. Many thanksIan