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
: 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:
Overview of FAT, HPFS, and NTFS File Systems
FAT32 provides the following enhancements over previous
implementations of the FAT file system:
- FAT32 supports drives up to 2 terabytes in size.
NOTE: Microsoft Windows 2000 only supports FAT32 partitions up to a
size of 32 GB.
- FAT32 uses space more efficiently. FAT32 uses smaller
clusters (that is, 4-KB clusters for drives up to 8 GB in size), resulting in
10 to 15 percent more efficient use of disk space relative to large FAT or
- FAT32 is more robust. FAT32 can relocate the root folder
and use the backup copy of the file allocation table instead of the default
copy. In addition, the boot record on FAT32 drives is expanded to include a
backup copy of critical data structures. Therefore, FAT32 drives are less
susceptible to a single point of failure than existing FAT16 drives.
- FAT32 is more flexible. The root folder on a FAT32 drive is
an ordinary cluster chain, so it can be located anywhere on the drive. The
previous limitations on the number of root folder entries no longer exist. In
addition, file allocation table mirroring can be disabled, allowing a copy of
the file allocation table other than the first one to be active. These features
allow for dynamic resizing of FAT32 partitions. Note, however, that although
the FAT32 design allows for this capability, it will not be implemented by
Microsoft in the initial release.
FAT32 Compatibility Considerations
To 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
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
: A FAT32 volume cannot be compressed by using Microsoft
DriveSpace or DriveSpace 3.
Converting to the FAT32 file system is one of the biggest
performance enhancements you can make to your Windows 98-based computer.
At 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 Drives
In 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:
- Click Start, point to Programs, point to Accessories, point to System Tools, and then click Drive Converter (FAT32).
- Click Next.
- Click the drive that you want to convert to the FAT32 file
system, and then click Next.
- Follow the instructions on the screen.
Microsoft 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.
information about FAT32, click the article number below to view the article in
the Microsoft Knowledge Base:
Common Questions About the FAT32 File System