Hey Frosty,
I few things to check.
Did you remove the multi media board or the simm at any time?
Did you clear or key the machine recently?
If you had the MM board off of the MPU check again that you did not bend any pins where the board plugs into the mpu.
Sometimes the simm chip gets a little corrosion on it's contacts lightly rub them with a pencil eraser and reinstall.
If you recently keyed the machine you just need to go into the multimedia sections under options/sound 3.2.6.4 , 5 , and 6. You want to set each of these to enhanced sounds. That should get you going again, If not post back with game theme.
Rich