I need help with the sims 2 on my pc.

Hello,
i am having a little trouble with the sims 2. I downloaded bon voyage, open for buisness and ikea home stuff and when i go in to play the sims 2 the picture when i move around is fine but then when i stop it goes all weird and it is hard to see any of the stuff that is in the neighbourhood or in a lot. I need help cause i really like playing the sims 2 but it makes it really hard when you cant really see anything. So if you know whats wrong or you thin you know how to fix it can you please tell me. thanks. The thing on the computer is windows vista and i have never had this problem before while playing the sims 2 on it.