My Sims 3 is lagging very badly I have 8 GB Vista 2 50 GHz and a 7550 Dual-Core Processor I just installed and its lagging horribly Why is it lagging

Because Vista is crap. I still have vista on my laptop, and it was the same. Make sure you don't have ANY other programs running while you play, and don't add any custom content, or remove any you have downloaded/installed. Good luck!