In NT 4, GetShortPathName did not care if the file existed - it would give the short path name anyway. This behavior was ...

In NT 4, GetShortPathName did not care if the file existed - it would give the short path name anyway.  This behavior was changed in NT 5 (Win2000) to reflect behavior of Win9x which will fail if the file does not exist. Setting this flag will provide the old behavior.