hey does anyone knows a (free) program to sperate voice and music and that you can save them both?

What you are describing is nearly impossible, unless the song was mixed in a very specific way, which almost noone does any more. You can attempt to make one or the other more clear over the other, but actually seperating them is nearly impossible with modern music. Some older recordings(50's, 60's) were mixed such that this was possible due to the use of the stereo spectrum, but things are way too mixed nowadays.

Krikkit is absolutely right. Out of interest, what was your plan with the two files? Create your own SingStar game?

Im sure if you contacted the record label they could provide you with vocals and instrumentals on seperate tracks. It wouldnt be free though, but if you plan on using commercial songs in your program you would probably already know this.

If its just for your own enjoyment im afraid its not possible. If you arent picky about what songs you want you can purchase kareoke albums.

Ps. If you know someone with singstar you could record the instrumental versions straight from the game.