Re: Error (0xc0000006)

Yes, it's only The Sims 3 games. All my other games (both on my computer and on my Origin account) start up fine.
I have Windows 7

Do you have the newest .net framework installed ? If so, try reinstalling it to make sure it's not corrupt.

When I tried downloading Version 4.5 (I think that's the newest version), it said "Download Could Not Occur: Same or higher version of .NET Framework 4.5 has already been installed on this computer."

Try uninstalling first and then reinstall.

I tried uninstalling and it said,

"Removal Did Not Succeed

.NET Framework 4.5.1 has not been removed from this computer because:

Fatal error during installation

For more information about this problem, see the log file.

For information about the most current version of the .NET Framework, see Windows Updates.

When you close this window, you will be prompted to send a problem report to Microsoft. For more information, see Microsoft Error Reporting Service."

Did you try starting the game from Origin? Did you try to start the game from the desktop icon? The only thing that comes to mind is there is some system damage or some corrupt data on the system drive. Try chkdsk /r /f first then try the Windows repair from the install image. Boot from the install dvd or image partition and try the repair option as detailed in the link - Windows error