I managed to do it. For those who are interested, you need to increase the speed rate of your sound files by 2 using a software like audacity before you try to convert them to ACM since the problem was that my audio files were played two times slower; and ignore the warning concerning the truncated error since it's not doing anything.
I think the problem was related to the ACM player which is known to have an incredibly high reading speed of 705 kb/s.
I tried what you wrote remake but it's not working at all since I wanted to use my musics on servers created by other people !!
And I guess the names and type of files associated with the different game locations is server sided.
By converting the files like I am doing I can play servers like
Requiem, Reloaded or FOnline 2 and put my own songs everywhere I want. I hope I answered your "first" question
Thanks Ghosthack and thanks
remake.