How to replace .ogg files?

[|BHC|Freddiex]

Hey Guys,

So I was messing around with the game files, modding the weapon skins and stuff, and thought I'd try playing around with the sound files. So I converted a few .mp3s to .oggs, and renamed them. However, even after the files have been replaced, the original soundbite still plays, why is this?

Any help would be greatly appreciated!
~|BHC|Freddiex

EDIT: I'm on Mac OS 10.6 (Snow Leopard)