POSIX requires a certain amount of functionality from the file system, such as the ability for a file to have more than one name (or hard links) and case-sensitive file naming. Neither FAT nor HPFS supports these features, which is another reason why a new file system was required for Windows NT. NTFS supports both hard links and case-sensitive naming. If you want to run in a POSIX-conforming environment, you need at least one NTFS disk partition on your computer.
You can run POSIX applications from any Windows NT file system. If the application does not need to access the file system, the application will run with no problems. However, if the application does require access to the file system, it might not behave correctly on a non-NTFS disk partition.