Registry Tip : NT's Long File Name (LFN) support

by Wayne Maples [Published on 20 April 2004 / Last Updated on 20 April 2004]

Enable long file name support in NT - background on LFN.

NT support long file names (LFNs) even under FAT. The File Allocation Tables are essentially unchanged; linked lists of 8.3 entries are still the core of the FAT file system. NT works around the 8.3 limitation by concatenating multiple 8.3 segments into a single long file name. For each thirteen chars in LFN, NT uses a single directory entry with a pointer to the next directory entry (for next 13 chars) if needed. When the LFN is completed, NT generates a short 8.3 compliant file name for use as an MS-DOS compatible "alias". To diable LFNs support in NT:

Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Control\FileSystem\
Name: Win31FileSystem
Type: REG_WORD
Value: 1 Disable Long Filename Support
Value: 0 Enable Long Filename Support

This could cause severe problems. Its probably one of those admin tweaks that one implements to save a few processing cycles but spend days working on odd symptoms due to the change. Not recommended.

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