As Said Above, A Licence Is Required To stop the police from being able to Take your Laptop & Music And put fines towards you.
But The Best Software To be honest I have found to Organise music, is iTunes....
And to Play It, Well Serato, VDJ, Tracktor, Are the main 3. And To Get hold of music, Well Beatport, iTunes' and even Amazon do mp3's for 29pence...
Stewart,