Electronic Arts periodically releases official patches for "The Sims 3" for the personal computer. These patches improve performance, fix issues and sometimes unlock new features. If you've downloaded and installed a patch that you weren't happy with, the only way to downgrade back to a previous version is to uninstall and reinstall your copy of the game. This is accomplished using native Windows tools.
Click the "Start" button.
Open "Control Panel."
Click "Programs and Features." Right-click on "The Sims 3" from the list on your monitor. Click "Uninstall" to launch the game's uninstall utility. Click "Next" to completely uninstall the game's system files from your computer. Do not select any additional options from the uninstaller -- this will keep your save games and preferences files in place.
Reboot your computer.
Insert your "The Sims 3" installation DVD into your computer. Click "Install" from the window that appears. Type your "The Sims 3" serial key (printed on the case the DVD came in. This is also the same key you used to originally install the game) into the utility and click "Next." Click "Finish" to reinstall "The Sims 3" on your computer, which will uninstall a version of the game that has not been patched.