...

...

Disassociate Library Files

Individual library files can be removed by disassociating them from their respective assembly. To disassociate a file, click on Disassociate library file in the Actions column (Figure 2). 

...

Using the Dissociate library file tool does not physically remove the file from the disk, but disassociates the file from the selected library file name. This, in turn, enables you to associate newer or improved version of the library file with the same library file name. If the goal is to physicall physically delete the library files from the disk, then all the projects using that library file must be deleted first.

...