I have been playing Sims 3 on this PC for about a year now and haven't had any problem. I opened it up yesterday and was glitching at the loading screen. Please see attached. I have uninstalled and reinstalled and I get this same result. I have even tried loading with just the base game and the same result.
@Williamss00 If you have any Razer software installed, please uninstall it and test. You can also try disabling it in the Task Manager, including any services listed in background processes, but I've heard from other users that this isn't always thorough enough. (I'm not sure why, since it should be enough, but that's what people are reporting.)
If that doesn't help, please run a dxdiag and attach it to a post.
Please also let me know whether you see the same issue in windowed mode. If you can't reach the option in the Main Menu, you can open options.ini, in Documents > Electronic Arts > The Sims 3, to set fullscreen to 0 (zero).