dual core isn't implemented in most programs yet, and particularly not in many games. Right now, you get faster prestanda with a non-dual core but with more Ghz for that single core. I.e. a dual core 3 GHz is slower than a single core 4GHz. That's bound to change, but it'll probably take at least 1-2 years or more until dual cores prestanda is used by most programs. If you use several programs at the time in Windows, you get a prestanda boost even today, but when running a single program you'll not notice any improvement from dual cores yet.