by Boikat » Sun Aug 02, 2009 7:23 pm
You have a few options.
Swap in a sound file from any twin engine passenger jet, like the A321. The sounds will not be authentic 737 sounds, however.
You could try a "repair" by loading Disk 1 for FSX. There should be a "repair" option. I've heard mixed opinions on the usefulness of the Repair option, but I've never used it, so your mileage may vary.
Search for "FSX, 737-800, sound" on google (or here at SimViation), and see if there are any hits for aftermarket sound sets.

"I reject your reality, and substitute my own" Adam Savage, Mythbusters