
Another alternative is to have Origin logged in on another computer and then launch it you'll be notified that you're logged in elsewhere and asked if you want to continue in off-line mode (my daughter and I experience this all the time). You can then re-enable the internet and Origin will remain offline. It will notify you that you are offline and ask for you to log in (even though you aren't online). You can temporarily disable your internet (easy on a laptop, not so sure about a desktop) and launch Origin.

MrsFlynn's instructions are perfect for going offline, but there's a way to launch Origin in off-line mode to start if that's your preference. If you purchased/installed through Origin, I have no idea if you can by-pass it. I use TS3.exe to by-passes the launcher, or I use Sims3Launcher.exe to see the launcher first. I don't currently have wifi at my house, and since I paid for it it would be cool if I could play it. I never had to install the games using the product keys, it just installed itself and I was able to play it around wifi. I don't use the expansion directory my files are in: \\\Program Files (x86)\Electronic Arts\The Sims 3\Game\Bin\. I bought the Sims 3 and a few expansions, and it won't let me play offline. However, I purchased and installed them prior to Origin (but I am able to play through Origin if I want).

I have two files that I use to play TS3 without Origin.
