I know that I have the same video card that you have and I recently needed to update the drivers. You can do that on the Nvidia website. I update them not because of Sims but because of another game that had higher expectations. Also Look at the other threads in this board you might not have enough ram. I know that Vista almost always needs more ram than a computer that uses xp. Why? I don't know but my guess would be something to do with virtual memory. I saw an estimate stating that Vista my need 3gb also I believe I read on here that the black screen could be a symptom of you processor not cutting and the computer shuts the program down because its overheating?
Based on my own computer knowledge and just reading about other peoples problems the above is my guess as to whats going on.