InstallShield Wizard Setup wont let me install my game

I had this same problem when I was installing The Sims 3 Seasons Expansion Pack, and I had found how to fix it and it worked, however that was a long time ago. Now I bought The Sims 3 Pets and the InstallShield Wizard  still says "Setup cannot continue because programs associated with The Sims 3 are currently running. Please stop these applications before attempting to run The Sims 3 Pets setup." I have tried going to task manager, then clicking the tab "processes" or whatever, and closing anything that says "Sims" running, DIDN'T WORK. I have tried restarting my computer, DIDN'T WORK. I think a Cache might have to be deleted, or at least someone who knows how to see what's running in the background and I can't find one thing. So HELP!