Hi Sonshine,
I don't think they necessarily meant to turn off your antivirus software and firewalls. They most likely were meaning to whitelist them. So the firewall and Antivirus software don't think Sims 3 is a virus or something along those lines.
As I've heard of that happening - the antivirus program thinking Sims 3 was a virus, when it's not. I completely understand you not wanting to mess with that!!
Anyway, I did some research on the problem and have something for you to try:
I'm assuming you want to go with the origin patch version 1.69? If so, go with the instructions listed below. If you're wanting to go with patch level 1.67 (disc version) try these instructions listed
in this thread.
Sims 3 - Uninstall/Reinstall - Origin version 1.691. Go to the Origin Games folder and click on Sims3Setup.exe.
2. When it gives you the option, do a custom install and direct it to install to C:\Program Files (x86)\Origin Games\The Sims 3
3. Now open up Origin and you will see that instead of saying "install", it now says "Play". Click on that.
4. Run the FordGT90Concept's Patcher -
http://modthesims.info/d/409829** It will install the patches for the earliest games that got left out of the super patch and help it work better.
5. Run the game to make sure things are going okay. If so, go to step 6.
6. If you have expansions/stuff packs to install, exit and restart Origin and then download and install your expansions and stuff packs.
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Reference Links:
The solution to your problem is HERE:
http://answers.ea.com/t5/The-Sims-3/quot-Origin-won-t-install-The-Sims-3-quot-THE-SOLUTION/m-p/1403740#U1403740Error During Startup
http://sims3.crinrict.com/en/2011/03/error-there-was-an-error-during-startup.html