Problems installing World of Warcraft

First off Before today World of warcraft has run perfectly fine but had a problem with a new patch(1.7.1) so i decided to reinstall the game.

Now i put the CD in and double click the install file, the icon does the fade thing to show its opening, the dock moves slightly for a split second, but then absolutely nothing happens.

I have no idea what to do... have tried several random things but I've got nothin...

Thanks in advance

Specs:
Dual 2.7
4GB of ram