I have read your other posts about this and the common denominator is: your game never fully installs from the DVD. Take it back for an exchange.
One more thing that may prevent the complete installation is the running of software utilities such as those by McAfee or Norton. They tend to take over your system and prevent you from doing anything. Had problems with McAfee security Suite on a clients PC with Vista, while trying to install software.
Hope you get it fixed for you are missing out on a REALLY great game!
