Since it uses 'They' i perceive the context as following: Speaking about certain (They...) applications (software), the sentence indicates that "those certain applications...." are not the usual ones that run (execute) on file systems as : FAT 32, NTFS (Windows machines) MAC OS file system (Apple Computers) UNIX File System (Linux- UNIX based computers) The above mentioned must be the file systems which can be considered 'general purpose' In a few words: Don't expect the certain application to run on Windows, Mac or LInux. I wonder what kind of an application may that be ! You got it from NASA or CIA? :)