Windows NT Removable Media Requirements and Limitations

This article was previously published under Q101626

Windows NT supports most removable hard disks and magnetic-optical disk drives. These disks are treated as hard disks because they must be partitioned and they are assigned a drive letter. However, Windows NT does not support write-once disk drives.

Windows NT supports removable media subject to the following restrictions:

• A removable hard disk can have only one primary partition. Extended or logical partitions are not supported.
• Windows NT supports only the Windows NT filesystem (NTFS) and MS-DOS-compatible (FAT) file system on removable media.
• The user cannot assign the drive letter for the device.
• Removable disks are not supported in a fault tolerant manner.
• You can install the Windows NT system files (the files contained in the WINNT directory) on a removable disk. However, the NT boot files, such as NTLDR and NTDETECT.COM, must be on the hard disk drive (fixed disk).
• If the paging file is located on the device or if the device has the NTFS installed, the media is locked until the system is shutdown.
• The FAT file system locks the media while it is in use and unlocks it after approximately 10 seconds of inactivity. NOTE: Windows NT supports a 20.8MB "floptical" disk as a floppy disk, not as a hard disk. Each write to a floppy disk is performed on a write-through cache basis and you can remove a floppy disk as long as the drive light is not on.