Hi guys i need to drop the key of a backing track whats the best way to do it
thanx
gary

Best? - more expensive and perhaps better solutions ... but what's at your immediate disposal included from X3 Studio / 2015 Professional and definitely worth a go is Melodyne Essential.
 
Apply it as a Region FX on the Audio backing track, leave it in 'percussive' mode (one line of blobs). Select the whole Melodyne track and drag it up or down. You can get pretty good results to say +/- 8 semitones (before it gets too muddy).

I have EZ PC DJ which is a Karaoke program.  I can change keys with it.  
I have a lot of Karaoke singer clients so it was needed. 
 
If you can't get it figured out, you can send me the file and I can change it to whatever key you want and send it back.
 

Audacity (free ware) has a very good module for doing what you want.

Cheers,
Jerry

^ +1 to Audacity... free, easy, quick.. but obviously the artifacts increase the more you move away from the original key.

Use Process > Transpose. Just make sure "Transpose Audio" is checked, and choose Radius Mix for Type.

And to add, going down in pitch has more issues than going up. Drums become muddy and the snare sounds like a cardboard box. And Bass goes into Sub Bass which not all playback systems can handle. 
 
Any Wave editor will work. Sonar too but it's faster in a wave editor.
Wave editor= Open , render,save. 
Sonar= Create template- insert audio track, import audio, three menu clicks and so on.. 

Cheers people Iv got a few options now

Up "1" or down "1" isn't a problem with Karaoke tracks using my EZ PC DJ program, even if it has background voices.  It can get ugly if its moved too far, up or down.

I would go with Craig's suggestion.
 
If you change keys and tempos frequently, you might consider a tool like this.  I have not used the current version, but the old version was pretty good about changing key and tempo, as well as mashing up, cutting, and splicing.
 
http://www.mixmeister.com/