Hallo.
Ive been reading and trying how to remove the vocal from a song without making chances of the instruments, but so far without luck.
Can you tell me what to do, please???
Thanks! 
There is a tutorial here: http://wiki.audacityteam.org/wiki/Vocal_Removal
If you need further help, please post in the forum section that is appropriate for you operating system and version of Audacity.
The Audacity wiki has an article on this subject: http://wiki.audacityteam.org/wiki/Vocal_Removal
– Bill