Well you biggest problem is in your first sentence. You have a Netbook. Those laptops are not meant for power, and sims 3 is a fairly system heavy game. Unfortunately, there really isn't much you can do. For the most part, once you purchase a laptop you are stuck with the video card it came with.
Most normal lower end laptops will have issues playing the game much less a Netbook. Netbooks just don't have the power. Sorry to be the bearer of bad news.