I upgraded to Windows 10 about a week ago, and then Sims 3 failed to load. So, I uninstalled everything and reinstalled the base game which works fine in compatibility mode. Unfortunately, I'm unable to run any of my expansion packs so I've had to stick with the base game for now but that really sucks because I've invested so much money and time into my expansion packs and the game isn't the same without them.
Anyway, I was on the phone with EA tech support three days ago and I was told that they're working on a solution to the problem. I hope it's soon.
I installed all of my sims 3 after the windows 10 update was complete. After downloading The Sims 3 original version it asked for an update. After that update all I did was download the expansion packs that I have and it works fine for me... I don't know if this helped...