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(The following was tested with Windows XP. Details may be different for other versions)
Caution: Partitioning and/or formatting your disk means that all files on that disk will
be erased forever. Do not attempt these steps unless you are quite sure there is nothing of value
on the disk.
FAT, FAT32 and NTFS (see Ref. 1) are the three most common file systems
used on PC's running MS Windows systems.
Contrary to what you might think, FAT is not the anti-diet file system, but is short for
"File Allocation Table", a file system devised for use with DOS (see Ref. 2).
It has a rather serious limitation that the largest disk can only be 2 GB, so it was later extended
to FAT32, a 32-bit variant, supported by Windows 95 OSR2 and later, capable of disks upto 2000 GB in size.
At the same time, between the late 1980's and early 1990's, Microsoft was working on an operating system
to replace DOS and the 16-bit versions of Windows, and this system was dubbed Windows NT (for New Technology).
This OS also had a completely new file system, called NTFS (NT File System), with several improvements
for storage efficiency, security, support for large disks, etc. (see Ref. 3).
The plan was to slowly phase out FAT and FAT32 in favor of NTFS, but due to widespread use and user demand,
MS decided to support FAT and FAT32 with newer systems as well, starting with Windows 2000 and extending to the
current Windows Vista.
With the exception of Windows NT, all NT based systems (2000, XP, 2003 and Vista) can read and write FAT32
file system disks.
And they can also format new disk partitions as FAT32 - or so I thought.
The Problem
I have an external USB hard drive (100 GB) which I use for moving files between computers.
The other day a user wanted to move some large folders from his older-model computer to another one, so
I offered the use of the external drive.
When we plugged in into the PC, it seemed to detect the device, but there was no additional hard
drive in WIndows Explorer.
I noticed his PC was running Windows ME, which is based on Win/9x, and does not recognize NTFS disks.
I confirmed this by plugging the USB drive into an XP system, and checking that its file system was indeed NTFS.
This did not seem a big problem, as XP could work with both NTFS and FAT32.
So I used Disk Management in XP to delete the existing NTFS partition, and (still within Disk Management)
attempted to create a new FAT32 partition in the same space.
I right-clicked on the now un-partitoned disk and selected "New Partition" (see Fig. 1)
Figure 1 - Creating a new partition
On the next dialog I asked the new partition to use all available space (100 GB) of the drive.
This is also the default.
Then I attempted to select FAT32 as the "File System", but ran into a problem, The only
available option seemed to be NTFS (Fig. 2).
Figure 2 - NTFS is the only choice.
I took the drive over to my new Vista system and tried creating a partition there, but got the same
choice - of NTFS alone (Fig. 3)
Figure 3 - NTFS is the only choice in Vista also.
What now?
A web search suggested that formatting FAT32 might be possible by booting from the Win 98/ME install CD, but that seemed
quite inconvenient, and it was very likely that booting from CD would mean the external USB disk would
not even be "visible".
I ran across an article from Microsoft (Ref. 4), which explained that
what I was attempting was impossible, i.e. the max size of a partition that could be formatted FAT32 on
an XP system is only 32 GB. Apparently this limitation is the same in Windows 2000, and as our tests have
shown, also in Vista.
To quote:
You cannot format a volume larger than 32 gigabytes (GB)
in size using the FAT32 file system during the Windows XP
installation process. Windows XP can mount and support
FAT32 volumes larger than 32 GB (subject to the other
limits), but you cannot create a FAT32 volume larger
than 32 GB by using the Format tool during Setup.
If you need to format a volume that is larger than 32 GB,
use the NTFS file system to format it. Another option is
to start from a Microsoft Windows 98 or Microsoft Windows
Millennium Edition (Me) Startup disk and use the Format
tool included on the disk.
To confirm this, I reduced the size of the partition to 32 MB (Fig. 4 below), about one-third the size of the disk.
Figure 4 - Reduce partition size to 32000 MB.
And sure enough, this time FAT32 appeared as one of the choices for file system (Fig. 5 below)
Figure 5 - Can now use FAT32.
A quick check confirmed that this is case on Vista as well.
Other than a cryptic "This behavior is by design", there is no explanation for this disappointing limitation.
The Solution
More web searching yielded a hint that Partition Magic may be able to format FAT32 partitions greater than
32 GB, but that is a commercial program I don't have.
Then I ran across a free downloadable program named Fat32Format from Ridgecrop Consultants
(Ref. 5) which completely solved the problem.
I started by downloading the fat32format.zip file (from Ref. 5), and unzipping the
contents into its own folder on the hard drive.
There is nothing to install, the fat32format.exe program can be run directly from the extracted executable.
But, before running fat32format, a partiton had to be created.
I launched Disk Management, and right-clicked on the 100 GB unallocated space on my external USB drive,
and selected "New Partition" (Fig. 6 below).
Figure 6 - Creating a new 100 GB partition.
In the next dialog I asked it to be assigned the drive letter F: (Fig. 7).
Figure 7 - Assign it drive letter F
Next, I told it to not format the partition at this time (Fig. 8).
Figure 8 - Do not format new partition.
When done, I was left with a healthy 93.16 GB partition, not yet formatted (Fig. 9).
Figure 9 - Partition not yet formatted.
I closed Disk Management, opened a command window, and started the fat32format program (Fig. 10).
Figure 10 - Starting fat32format.
Note that I specified the drive letter (F:) on the command line.
I typed "Y" for the first warning, to continue.
The formatting started at this point (Fig. 11)
Figure 11 - Fat32 format in progress.
Less than a minute later, it was done (Fig. 12)
Figure 12 - Fat32 format done.
Checking disk properties for drive F: in Windows Explorer shows the formatting worked correctly. (Fig. 13)
Figure 13 - Fat32 format with 100 GB space.
Discussion
While fat32format solves the problem, a few questions remain, mainly, why is there a 32 GB limit
on FAT32 partitions in Windows XP?
Is it there to encourage people to switch to the more efficient and newer NTFS file system?
Is it due to poor programming or design?
Is it because FAT32 partitions become slow at large sizes?
If you know the answer please let me know.
FAT32 is probably here to stay for a while because it is widely used in external devices such as USB disks and
flash memories.
The main reason for this is that many modern devices (cameras, music players etc.)
can read/write FAT32 disks but not NTFS.
Update Apr. 2012: I tried the above method (i.e. using fat32format) on Windows 7 and it works fine there also.
References
- Choosing between NTFS, FAT, and FAT32 -
http://www.microsoft.com/.../choosing_between_ntfs_fat_and_fat32.mspx
- FAT - File Allocation Table -
http://en.wikipedia.org/wiki/File_Allocation_Table
- NTFS - New Technology File System -
http://en.wikipedia.org/wiki/Ntfs
- Limitations of the FAT32 File System in Windows XP -
http://support.microsoft.com/kb/314463/
- Ridgecrop Consultants fat32format -
http://www.ridgecrop.demon.co.uk/index.htm?fat32format.htm
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