Need more neighborhoods to contain all of your Sim families?  Well by editing a single file you can create up to a total of 99 neighborhoods to use in the game.

1. Open Windows Explorer.
2. Navigate to the directory into which you installed the game.
3. Look for a folder named "TemplateUserData".
4. Right-click on the folder and select "Copy".
5. Right-click elsewhere in the window displaying the contents of your The Sims game folder and select "Paste".
6. Right-click on the new folder and select "Rename".
7. Rename the folder to "UserDataX", where X is any number up to 99.  Make sure you do not already have a folder named with the number you select.
8. Start The Sims.

That's all there is to it!