System files mft record numbers.  All these files are always marked as used
in the bitmap attribute of the mft; presumably in order to avoid accidental
allocation for random other mft records.  Also, the sequence number for each
of the system files is always equal to their mft record number and it is
never modified. (Only $MFT has a sequence number of 1, rather than 0.)

FILE_$MFT       = 0,	/* Master file table (mft).  Data attribute
			   contains the entries and bitmap attribute
			   records which ones are in use (bit==1). */
FILE_$MFTMirr   = 1,	/* Mft mirror (copy of first four mft records)
			   in data attribute. */
FILE_$LogFile   = 2,	/* Journalling log in data attribute. */
FILE_$Volume    = 3,	/* Volume name attribute and volume information
			   attribute (flags and ntfs version).  Windows
			   refers to this file as volume DASD (Direct
			   Access Storage Device). */
FILE_$AttrDef   = 4,	/* Array of attribute definitions in data
			   attribute. */
FILE_$root      = 5,	/* Root directory. */
FILE_$Bitmap    = 6,	/* Allocation bitmap of all clusters (lcns) in
			   data attribute. */
FILE_$Boot      = 7,	/* Boot sector (always at cluster 0) in data
			   attribute. */
FILE_$BadClus   = 8,	/* Contains all bad clusters in the non-resident
			   data attribute. */
FILE_$Secure    = 9,	/* Shared security descriptors in data attribute
			   and two indexes into the descriptors.
			   Appeared in Windows 2000.  Before that, this
			   file was named $Quota but was unused. */
FILE_$UpCase    = 10,	/* Uppercase equivalents of all 65536 Unicode
			   characters in data attribute. */
FILE_$Extend    = 11,	/* Directory containing other system files (eg.
			   $ObjId, $Quota, $Reparse and $UsnJrnl).  This
			   is new to NTFS3.0. */
FILE_reserved12 = 12,	/* Reserved for future use (records 12-15). */
FILE_reserved13 = 13,
FILE_reserved14 = 14,
FILE_reserved15 = 15,
FILE_first_user = 16,	/* First user file, used as test limit for
			   whether to allow opening a file or not. */