Does somebody know about a program to separate the voice of the sound of a song?
Have you searched here (http://www.google.com)?
It's pretty difficult to remove something from a recording without seriously screwing up the rest of the mix. I bet even a professional sound engineer would have some trouble removing vocals.. I wouldn't count on finding a program on the internet that can do it.
You can use certain filters, for example on Winamp, but it does screw up the entire thing. Why, are you ripping a song? If so, use a Matrix theme or something without words. :P
GoldWave can do it quite nicely depending on the song... Effects -> Stereo -> Reduce vocals... There are several presets which give different results... But it's not perfect. :(