Description of the FAT32 File System
This article was previously published under Q154997
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242450 (http://support.microsoft.com/kb/242450/EN-US/) How to Query the Microsoft Knowledge Base Using Keywords
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This article describes the FAT32 file system that is included with Windows 95 OEM Service Release 2 (OSR2), Windows 98, and Windows Millennium Edition (Me).
Windows 95 OSR2, Windows 98, and Windows Me include an updated version of the FAT file system. This updated version is called FAT32. The FAT32 file system allows for a default cluster size as small as 4 KB, and includes support for EIDE hard disk sizes larger than 2 gigabytes (GB).
NOTE: Microsoft Windows NT 4.0 does not support the FAT32 file system. For additional information about supported file systems in Windows NT 4.0, click the article number below to view the article in the Microsoft Knowledge Base:
100108 (http://support.microsoft.com/kb/100108/EN-US/) Overview of FAT, HPFS, and NTFS File Systems
FAT32 FeaturesFAT32 provides the following enhancements over previous implementations of the FAT file system:
FAT32 Compatibility ConsiderationsTo maintain the greatest compatibility possible with existing programs, networks, and device drivers, FAT32 was implemented with as little change as possible to the existing Windows architecture, internal data structures, Application Programming Interfaces (APIs), and on-disk format. However, because 4 bytes are now required to store cluster values, many internal and on-disk data structures and published APIs have been revised or expanded. In some cases, existing APIs will not work on FAT32 drives. Most programs will be unaffected by these changes. Existing tools and drivers should continue to work on FAT32 drives. However, MS-DOS block device drivers (for example, Aspidisk.sys) and disk tools will need to be revised to support FAT32 drives.
All of the Microsoft bundled disk tools (Format, Fdisk, Defrag, and MS-DOS- based and Windows-based ScanDisk) have been revised to work with FAT32. In addition, Microsoft is working with leading device driver and disk tool manufacturers to support them in revising their products to support FAT32.
NOTE: A FAT32 volume cannot be compressed by using Microsoft DriveSpace or DriveSpace 3.
FAT32 PerformanceConverting to the FAT32 file system is one of the biggest performance enhancements you can make to your Windows 98-based computer.
Dual-Boot ComputersAt this time, Windows 95 OSR2, Windows 98, Windows 2000, and Windows Me are the only Microsoft operating systems that can access FAT32 volumes. MS-DOS, the original version of Windows 95, and Windows NT 4.0 do not recognize FAT32 partitions, and are unable to boot from a FAT32 volume. Also, FAT32 volumes cannot be accessed properly if the computer is started by using another operating system (for example, a Windows 95 or MS-DOS boot disk).
Windows 95 OSR2 and Windows 98 can be started in Real mode (for example, to run a game) and can use FAT32 volumes.
Creating FAT32 DrivesIn Windows 95 OSR2, Windows 98, and Windows Me, if you run the Fdisk tool on a hard disk that is over 512 megabytes (MB) in size, Fdisk prompts you whether or not to enable large disk support. If you answer "Yes" (enabling large disk support), any partition you create that is larger than 512 MB is marked as a FAT32 partition.
Windows 98 and Windows Me also includes a FAT32 conversion tool that you can use to convert an existing drive to the FAT32 file system. To use the conversion tool, follow these steps:
Support BoundariesMicrosoft will support the functionality of the FAT32 file system for error-free reading, and saving of files either in Real mode or Protect mode. Microsoft supports the Real-mode and Protected-mode tools that are included with Windows 95.
For legacy (older) programs that cannot be installed on a FAT32 volume, or do not properly save files or read them, you must contact the manufacturer of the software package.
NOTE: Although the FAT32 file system supports hard disks up to 2 terabytes in size, some hard disks may not be able to contain bootable partitions that are larger than 7.8 GB because of limitations in your computer's basic input/output system (BIOS) INT13 interface. Please contact your hardware manufacturer to determine if your computer's BIOS supports the updated INT13 extensions. For additional information about FAT32, click the article number below to view the article in the Microsoft Knowledge Base:
253774 (http://support.microsoft.com/kb/253774/EN-US/) Common Questions About the FAT32 File System