If you need your product key for "The Sims 3," you'll have to look in one of several different places depending on where you purchased the game. If you're unable to locate the original box for a retail copy, you're not out of luck yet; you can still check your registry for the key if the game is still installed.
Finding a Steam Product Key
With thousands of computer games available through the Steam client, Valve makes it straightforward to find a product key for games purchased through the store. Sign in in to your account on the client, then select "Games" in the menu above. Right-click "The Sims 3" and select "View CD Key." A dialog box will pop up and display the key for the base game. Since Steam doesn't list expansion packs separately from the base game, however, you can't find Steam product keys for any additional packs you purchased. Additionally, you can only obtain a product key for a game currently installed on the computer.
Product Keys in Origin
The same company that published "The Sims 3" also developed the Origin client. If you've purchased the game on Origin, you can find the product key regardless of whether it's installed or not; just hover over "The Sims 3" in "My Games." When a pop-up box appears, click the "Information" button to see expanded details about your purchase, including the product key. Unlike Steam, Origin lists expansion packs separately for its games, meaning you can find a product key for each independent purchase.
Retail Copies of The Sims 3
Physical copies of "The Sims 3" have the product key listed on the back of the manual. If you're like any other gamer, you probably have some reason to worry about losing that manual; Origin allows its users to turn retail copies of games into digital copies just by entering the product key while logged in. While it's still worth holding onto the disc to bypass having to download the game before installing it, creating a digital copy secures the product key in a readily-accessible place.
Trying the Windows 8 Registry
If you already lost the manual but didn't get around to uninstalling the game, the registry will be your savior. Pressing "Windows+R" opens the Run box, where you can type "regedit" and press "Enter." If prompted, type in the administrator password for the computer. You can find the product keys for each individual expansion pack and the base game under the following path listed as "Data":
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