Music software

Here's the gen...

Traktor - DJ tool, good for DJing with MP3s so I'm told. Haven't used it myself.

Acid - Great for doing full length pre-recorded DJ sets and cut n shuts.
Also good for remixing tracks if your just cutting loops and rejigging them.

Soundforge - It's for sample/track audio manipulation. ie. Very minute
audio adjustments, mastering, normalising, etc.

Ableton Live - Like a cross between Acid and Traktor. Great for doing
live rejigging with pre-recorded tracks cut into loops.

To actually write tunes I'd advise something like Reason, FL Studio (my
fave), or Project 5 if your a beginner as they are all dedicated soft
studios and have everything u need built in. If your more serious then
go for something like Cakewalk or Cubase SX.

iain