A problem was present in the query parser of Copernic in version 8.0.0 which prevents searching using an exact phrase in the "System Folder" refinement if the folder starts with certain specific drive letters like C:\ or D:\.
This problem only affects documents indexed with a version of Copernic earlier than 8.1.0. All documents indexed with version 8.1.0 or later are not affected by this problem.
If you perform a search similar to "C:\Folder\SubFolder" in the "System Folder" refinement using quotes and no results are returned, remove the drive letter portion of the search term and results should appear.
Ex: Instead of searching for "C:\Folder\SubFolder", search for "Folder\SubFolder"