@Leslie544 I've split your post into its own thread, since the other thread was several years old.
Please make sure your computer has .NET Framework 3.5 enabled. Hit Windows key-R and enter "appwiz.cpl" without quotes. In the File Explorer window that appears, click "Turn Windows features on or off." You'll see this:
.NET 3.5 is right at the top. If the box next to it isn't filled in, click it, let it install, restart your computer, and try to launch Sims 3 again.
If this doesn't help, please run a dxdiag and attach it to a post.
https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/
And please also attach a screenshot of the message you're getting.
