How do I transfer my current Sims 3 game to a new computer?

Please register all your Sims 3 titles on the Sims 3 website. Read here how to do this:

http://answers.ea.com/t5/The-Sims-3/Information-How-to-Register-The-Sims-3/m-p/387162

On your new computer, please download and install the Origin client:

www.origin.com/download

Log into the Origin client with the same account (= email and password) that you use for the Sims 3 website. You can now download and install all your Sims 3 titles from the Origin client.

Many people are already playing The Sims 3 on Windows 8. If you have any issues with that, just use the search function here and you will get a lot of helpful threads:

http://answers.ea.com/t5/forums/searchpage/tab/message?filter=labels%2Clocation&location=forum-board%3Athe-sims-3

Please remember to save all your games to an external hard drive or a USB stick if you want to continue with your old games.