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I am using Windows XP now. Is there any way to convert a NTFS partition to FAT32 safely? A simple solution that doesn't involve backing everything up would be better.

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migrated from serverfault.com Oct 9 '10 at 16:48

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5 Answers

Here's my answer - don't do this at all, seriously, forget about it. If you had to I'd be tempted to just copy/backup-restore the data from one drive to another rather than risk all my data to a needless conversion. Either way don't do it.

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I can't upvote this enough. –  gWaldo Oct 9 '10 at 11:25
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+1, There's no good reason to do this. –  Chris S Oct 9 '10 at 17:50
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+1. There are ways to do it, but I wouldn't recommend them. –  David Spillett Oct 9 '10 at 18:15
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I'll get my harping on done first: no filesystem-wide operation like that should be performed without some reliable form of backup. Really. Seriously. How annoyed would you be if something went wrong and all that data was lost?

There is no way that I am aware of to convert from NTFS to FAT32 (or anything else for that matter) directly inplace. If the reason you want an inplace conversion is that you do not have another device with enough free space to copy the data onto then there is a way of converting in-place less directly but it is long winded:

  1. Delete anything you really don't need to keep from the NTFS partition and clear the recycle bin - that may make the following take less steps.
  2. Use a tool like gparted's live CD or Partition Magic (if that is still an available product? I've not heard much of it for a while) to resize the NTFS partition as small as possible.
  3. Using the same tool, create a FAT32 partition in the space vacated by the now truncated NTFS one.
  4. Move as much as you can from the NTFS partition to the FAT32 one as will fit.
  5. Resize the NTFS partition to as small as it can go again (now you have freed some space by moving stuff to the new partition), or if it is now empty just remove it.
  6. Move the FAT32 partition as close to the beginning of the disk as you can (i.e. so it starts at the end of the NTFS one if still there or the start of the disk) so it moves to the space vacated by the now shrunk/removed old partition and then resize it so it takes the now freed space towards the end of the disk.
  7. Repeat steps 4, 5 and 6 until everything is moved to the new partition and the old one is gone.

I wouldn't actually recommend this though for a number of reasons:

  • It will take far longer than copying the data to a backup (or refreshing your existing backup - you do keep backups of your important data, don't you? (I know I said I'd finish harping at the top this answer, but I couldn't help myself - if your data is important then keep backups, if it isn't just delete it and stop worrying!)), reformatting the existing partition to the desired format and copying the data back.
  • There are many filesystem wide operations that could kill your data if something (human error, software failure, hardware failure, power cut, ...) goes wrong, so if you don't have good backups the operation is risky and if you do have good backups see my point above about the overall speed of the operation.
  • You might get half way through and discover something that won't copy (a file larger than 4Gb for instance) or that because of the inefficiencies of the FAT32 filesystem you data takes more space that way so there isn't actually room for it in that format. This is particularly problem for lots of small files: NTFS can store them in the directory structure where they waste very little space but in FAT32 they must have a block to themselves so a 10 byte file will effectively take a couple of tens of bytes under NTFS but up 32,768 under FAT32 (for filesystems above 32Gb in size FAT32 uses 32Kbyte allocation blocks). The lack of granularity in FAT32's space allocation method leads to much wasted space for lots of files whether they are small or not: each file will wast on average 16Kbyte on a large FAT32 filesystem but 2Kbyte on a similarly sized NTFS one - see here for more information on cluster sizes for the various MS fileystems.
  • This definitely will not work, at least without some extra jiggery-pokery, for system partitions.
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+1 for mentioning how it can be done, and why it should not be done –  sleske Oct 9 '10 at 19:29
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Generally, this doesn't work, because FAT32 has a lower limit on file size and overall filesystem size.

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Partition Magic 8 and later can apparently do it, though I've never tried.

Regardless I would suggest that doing this without a full (tested) backup is foolhardy, any time you're changing the file system there's always a risk you'll end up losing everything. If your power fails during the conversion you've lost everything, if the computer crashes you've lost everything, etc.

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Microsoft CONVERT utility is a one way trip.

You could backup your data and restore on a FAT32 partitition or create a FAR32 partition and XCOPY/ROBOCOPY the files.

The good old Partition Magic did the NTFS->FAT conversion.

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He means one-way trip –  gWaldo Oct 9 '10 at 11:24
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