Remixing a Song

Hi,what program or programs or maybe its in Sonar already do you use to get that radio sounding remix of a song?I guess like DJ stuff where a song sounds completey  different but has the orginal vocal,drum,bass riff,that iceolates one sound from a song like vocals,drums,guitar.I've tried those free online ones and they dont seem to do a good job.You can clearly hear stuff still playing in the back ground like when you just want to capture the vocals,then add your own drum beat behind it.What program can i buy that does this sort of tooling on a professional lvl.Or is a external machine that does this stuff?

I've done a lot of unofficial remixes that way, but its not the best way as Loptec says best to get the original vocal track if you can, falling that at least an acoustic version of the song or even 2 exact copies of the song one with vocal and one instrumental, but they must be identical and use the phase inversion trick, works well most of the time to isolate the vocal. You could also do a search for "Studio Acapellas" on google theres are a lot online but not always legal. Also do a search for "remix competitions" as some top names offer the stems officially for download. For official remixes you will be given the stems to work with:-)