JSI Tip 0288 - How does Windows NT assign drive letters?

Windows NT first assigns drive letters that you configured in Disk Administrator (Windisk.exe) by selecting the Volume and choosing Tools/Assign Drive .. (assuming the partition is still valid).

If there is a primary partition on the first hard drive marked as active, it gets the first available drive letter, otherwise, the first available drive letter is assigned to the first recognized primary partition.

This process is repeated for all hard drives in the system. Please note that if you have multiple controllers in your system, the drive letter ordering is based on the order in which the device drivers are loaded by Windows NT.

Once the letters have been assigned to the first primary partitions on all drives in the system, letters are assigned to the recognized logical disks in the extended partitions using the same scheme as outlined above, starting with the first drive in the system.

After all of the logical disks in the extended partitions are assigned letters, one last scan is made of the drives, and letters are assigned to any remaining recognized primary partitions.

Some removeable media devices are considered to be hard drives and participate in the above.

Lastly, removeable media devices (CD-ROM) are assigned.

If your new JAZ drive is messing up your drive letters:

Remove the JAZ
Run Windisk and assign drive letters to all other devices
Attach the JAZ

Upon booting, you will find that the JAZ drive has the next available drive letter.

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