Tmoose,
SolidWorks perfers to have write access to all the models in what ever it is you have loaded. This is awkward, and I recommend turning the feature off.
Pull down Tools->Options...
When the window comes up, select the System Options tab and click on External References. Turn ON the button for "Don't prompt to save read-only" referenced document (discard changes)".
Now, SolidWorks will not complain when you use read-only files. This allows you to work with other designers. It allows you to treat existing parts and assemblies as a design library.
The first guy to load files gets write access to everything that is writeable. You can ensure that the guy who uses the top-level files comes to work late, or, you can do something with the ACLs (permissions) in Windows. Take a look at the file properties in Windows Explorer.
JHG