Sims 2 Weird Screen Thingy?(Details)?

I have a Windows Vista and I know it isn't compatible with the Sims 2 and all, but I got the patch for it and everything. So, I go onto the sims 2 and it's all fine. I can make a family and play around with their lives and everything and I can build and the loading times are normal. But there is just one really annoying problem, whenever I buy a huge lot, like for my legacy challenge, the screen frequently goes black and then it turns into this blue color and basically loads and then it's fine. It does this a lot. It also does it when I build a medium sized home, or play with a huge house and sometimes at community lots. I couldn't find anything about this problem and need help with the black screen-blue screen loading thingy! (sorry not sure what to call it)