Default Changing Default Click sound for keypresses

Hello,

Anyone know how to change the default keypress sound on the 750? I've turned on Hardware buttons "soft" in sounds and notification but would like to change from the click to something not so annoying.

I've already changed the MenuSel, MenuPop, and hwandsw wav files but don't know what this file is called or whether it's a reg key that needs to be changed.

TIA