Pappie, I recommend you buy Traktor (or Traktor Scratch if you want a vinyl interface). Traktor provides the closest approximation of djing out of all the software i've used.
I also recommend you get a good external midi controller to use as a mixer. i'm using one that looks like a regular dj mixer but controls the software. these are pretty common now if you search for midi dj mixer or something similar.
here are a couple links about Traktor, both include info about controllers/soundcards etc.
http://www.beatchemistry.net/wiki/tiki-index.php
http://www.native-instruments.com/fo...play.php?f=105