Sound's broken... again...

[iBeatz]

Okay, this has happened to me before a few times, but now it's completely unfixable. My sound for Graal has gone, and I seem to have no way to turn it on again.
Graal won't even show up as an application when I look on the volume mixer. There's nothing wrong with my F3 options, they're all at maximum, and I've tried setting tryloadsoundson64bit to true, but nothing seems to be working.

Can anyone shed a little light as to how I can fix this? I'm using Vista.