I'm not very used to those kind of things, but i found a way to make it worked. Apologises for my English, i'm not very good, so writhing about a subject i don't know is very hard.
Go to your "commend invite" ( don't know the English for it, it's in you accessory menu on windows XP assuming you're running under windows ). Move to your folder where the mpqx.exe is. If you don't know how to do it, use the commend "cd <folder's name>" to go in, and "cd .." to go at the parent directory.
Once you're here just type "mpqx.exe -F:\DIABDAT.MPQ" Assuming your cd drive is F. It should work.
Don't forget to change the diablo.ini file.
Edit : Well, actually, i've got a sound files which seems correct, with a lot of directories like monster and music. All with some working wav files but the music don't seems to work in game ( even with the ini file correctly changed )/