Converting FAT Partitions to NTFS—or Maybe Not?

You probably know that you can use the CONVERT.EXE command-line utility to convert a FAT (File Allocation Table) formatted partition to the more efficient and secure NTFS (New Technology File System) format. But did you know that you could cancel an NTFS conversion that's scheduled to occur the next time the system reboots?

In this article, we'll show those of you who are unfamiliar with CONVERT.EXE how to use the utility, and we'll explain how it will schedule a conversion to occur at system restart. Then we'll take a closer look at how Windows NT converts file systems during installation. Finally, we'll explain how to cancel a scheduled FAT-to-NTFS conversion.

Using CONVERT.EXE

To use the CONVERT.EXE utility to convert a FAT partition to NTFS, open a Command Prompt or Run dialog box and enter the command

CONVERT X: /FS:NTFS

where X is the drive letter for the FAT partition that you want to convert. If the target drive doesn't contain a folder that the system is currently using (such as the boot partition or the partition containing a Microsoft Exchange Server's Information Store), CONVERT.EXE will perform the conversion immediately. The conversion leaves the partition's data intact but applies default local NTFS permissions to folders and files. However, if the target partition contains the system root or if the operating system or a service is using data stored on the partition, CONVERT.EXE will display a dialog box shown and schedule the conversion to occur at reboot.

FAT is always first

Even if you're already familiar with the CONVERT.EXE utility, you may be surprised to learn that the Windows NT 4.0 Setup program performs a file-system conversion if you opt to install the operating system on an NTFS partition. During the text-based portion of the setup process, the Setup program always formats the NT's boot partition as FAT. Then, when you reboot the system to enter the graphical portion of the installation process, Setup converts the boot partition to NTFS before starting its GUI (Graphical User Interface). If you carefully watch the blue, text-based Setup screens that appear before the Setup program starts its GUI, you'll see Setup report that it's converting the file system.

Whoops! Cancel that!

There's nothing quite like the feeling that passes over you when you realize that you've just done something that could result in a dozen, if not hundreds, of E-mails or phone calls from users who are unable to access vital system resources. It's important to remember that the CONVERT.EXE utility only provides a one-way ticket from FAT to NTFS and that DOS clients are unable to access NTFS partitions without installing additional software. If you've used CONVERT.EXE to schedule a conversion for the wrong FAT partition, you'll dread the fact that a system reboot will require you to delete the partition, then re-create it and format it as FAT, and, finally, restore its data from backup. While you'll never want to find yourself in such a position, it's good to know that a relatively simple Registry hack can save the day if you do!

Please note: Even simple Registry edits can have potentially disastrous results if performed incorrectly. Make sure that you have a good Registry backup before implementing this technique. As always, use the Registry Edit tool cautiously, and at your own risk.

To cancel a scheduled NTFS conversion, open the Registry Editor, REGEDT32.EXE, and search HKEY_LOCAL_MACHINE for the subkey

\System\CurrentControlSet\Control\Session Manager

You'll find that this subkey's BootExecute entry reads

Autoconv \DosDevices\X: /FS:NTFS

where X is the drive letter for the partition that you mistakenly scheduled for conversion. Change the subkey's BootExecute entry to

Autocheck autochk *

Save your Registry changes and exit the Registry Editor. Then you can safely restart your system without fear that Windows NT will convert the partition to NTFS.

Important things to know about converting FAT to NTFS

You can only use CONVERT.EXE to convert FAT to NTFS, not vice versa.
Some clients will require special software to access NTFS partitions.
If a file system conversion is scheduled to occur at system restart, you can edit the Registry to cancel it if necessary.

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