First, I assume that you want to make changes to the mod's set of music, so you will first want to extract these files and place in the music folder. Get the IDX extractor
http://www.twcenter.net/forums/downl...?do=file&id=32. Extract the files and copy xidx.exe and extract_sounds.bat to your C:\...\SEGA\Medieval II Total War\mods\Stainless_Steel_6\data\sounds\. Run the extract_sounds.bat file. This will extract the sounds to folders in a new 'data' folder (oddly I could not get this to work at a higher level folder, even though it would make sense); the extracted music, then, will be located at C:\...\SEGA\Medieval II Total War\mods\Stainless_Steel_6\data\sounds\data\sounds\music\. Copy the files in this folder over the contents of the actual folder C:\...\SEGA\Medieval II Total War\mods\Stainless_Steel_6\data\sounds\music\.
Now, say you want to replace a certain track... oh, let's say (Campaign_Map)_Erin_04.mp3 (the pseudo-Middle Eastern pop song screaming 'carry me across the sea'). Find a track you want to replace it (if you want to remove it, create an mp3 of just a few seconds of silence), and copy the desired track to some middle ground (your Desktop, for example). Rename it (Campaign_Map)_Erin_04.mp3 , then copy the renamed track into the music folder, replacing the original (Campaign_Map)_Erin_04.mp3 . Now, go to the sounds folder, and delete just Music.dat (I don't think it is necessary to delete the IDX folder in these circumstances). The next time that you start the game, it will rebuild Music.dat automatically and you will hear the changes.