By Dervish / Last Updated May 12, 2023

The issue: drive letter not available 

Drive letters are alphabetical identifiers for all the drives on the computer, such as internal hard disks, optical drives, SD cards, and external USB drives. If a drive loses its drive letter, you can’t directly access files saved in it and all programs relying on the drive letter can’t run properly.

Usually, Windows assigns drive letters for each drive it detects automatically. You may assign drive letters manually in Disk Management under specific circumstances. Here is a real case:

“I just upgraded from Windows 7 pro to Windows 10 pro and many of my drive letters were changed. I can't change them back using Disk Management because the letters I need are not available to select from. All of my applications point to a drive &quo and that letter is not available. Only letters available are: I, L, M, N, P, Q, R, S, T, & V.
This needs to be fixed. I can't spend lots of time reconfiguring my programs and shortcuts to point to a new drive letter.”

This user can’t assign drive letter in Disk Management because the letter D is not available. How comes the issue of drive letter not available?

Why would a certain drive letter become unavailable?

If you find a certain drive letter missing from the list of available drive letters in Disk Management, it could be caused by:

● You have permanently assigned drive letter for an external hard drive, so the letter is reserved for the drive although it is removed.

● The drive letter is occupied by a hidden removable device or DVD/CD-ROM.

Then, how to free up a drive letter currently in use?

How to fix the drive letter not available issue

To fix unavailable drive letters, you may need to make some modifications in Registry. Following are the detailed steps:

1. Press Windows Key + R to open the Run dialogue. Type regedit and press Enter or click “OK” to open the Registry Editor.

2. Expand the entries on the left-hand pane to navigate to the following path:


3. Right-click on the device with the drive letter you want and select Rename. Change the letter to any other unused letter to free up the current one.

Registry Editor

4. Close Registry Editor and restart your computer.

The unavailable drive letter should be released after rebooting. The next thing to do is to assign the released letter to the drive as you want.

Assign drive letters in Windows with a powerful freeware

Since you already know how to assign drive letters in Disk Management, I’d like to introduce a powerful freeware to you, which can be used as an alternative. It is AOMEI Partition Assistant Standard.

As a specialized partition manager, it can not only help you change drive letters but also change partition type ID. It enables you to resize, move, merge and format partitions with just a few clicks. It supports all Windows PC operating systems like Windows 11/10/8.1/8/7/Vista/XP. Now download it and follow the instructions below to assign drive letter for a particular drive via AOMEI Partition Assistant:

Download Freeware Win 11/10/8.1/8/7/XP
Secure Download

Step 1. Install and launch AOMEI Partition Assistant. Right-click the drive to which you want to assign a drive letter, select “Advanced” and then “Change Drive Letter”.

Change Drive Letter

Step 2. Select the released drive letter in the pop-up window.

Choose New Drive Letter

Step 3. Click “Apply” to view pending operation and then “Proceed” to commit the operation.



When you encounter the issue of drive letter not available in Windows 11/10/8/7, you can fix it using Registry Editor. To assign drive letter for a particular drive, you can choose Disk Management or AOMEI Partition Assistant Standard. If you upgrade to Porfessional version, you can enjoy more functions, such as converting system disk between MBR and GPT, erasing SSD, etc.