As you may know, Small Business Server 2003 requires that you keep the default Organizational Units (OUs) within Active Directory that are created during the initial setup of SBS. Modifying even the names (ie, changing MyBusiness to some other less non-descript name) will cause all sorts of things to go wrong with your server and your domain. Even though you are required to keep the SBS order to your Active Directory, you can still use OUs to organize your users and to apply specific Group Policies to certain groups.
First you will need to create the new OU in the proper SBS-defined location, which is within the Users container directly under MyBusiness. Since all of the SBS default group policies are linked at the domain level, there’s no benefit to placing the OU anywhere else in the Active Directory structure. But, by creating it within the MyBusiness\Users Container, your new OU will work just great with SBS’s management tools.
After creating the OU, the next step is to create a User Template which will be used when adding new users via SBS’s Add User Wizard. User Templates ensure that you have all the proper settings applied to a new user without having to manually tweak each item. Because you’ve created a new OU, there will be this additional OU selection screen in the Add Template Wizard that you otherwise wouldn’t see:
You’ll note that once the first additional OU is created, you can create other ones on the fly by clicking on the "Create new OU…" button.
You can then create any Group Policy Objects you like and link them to the specific OU for which they apply. Of course, creating additional Computer OUs would be done in much the same way with any new OU residing within the MyBusiness\Computers container.