How to Change an OS Drive From DOS

Every drive on your computer is assigned a unique letter, with almost all computers assigning the main hard drive the letter "C." Windows provides system tools that allow you to change the letter assignment from within the system; however, you can also change a drive letter using MS-DOS, or the Command Prompt. This is useful if system errors are preventing you from opening the system tools necessary to change your drive letter.

• 1

  Open the "Start" menu, then type "CMD" into the search box and press the "Enter" key to launch the Command Prompt.

• 2

  Type "cd\" and then press "Enter."

• 3

  Type "edit c:\autoexec.bat" and press "Enter" to open the AutoExec.Bat window.

• 4

  Scroll down and locate the line labeled "MSCDEX," then type "/L:D" to set the drive letter to "D." Alternatively, the drive can be set to any letter, D through Z. Press the "Alt" and "F" keys simultaneously to exit the window, and choose "Yes" to save the settings.

• 5

  Type "edit c:\config.sys" in the Command Prompt and press the "Enter" key to open the Config.sys window.

• 6

  Scroll through the Config.sys window and locate any entry labeled "LASTDRIVE=x," with "x" being the old drive letter. Change this to a letter later in the alphabet than your highest drive. For instance, if your new drive is assigned the letter "G," the "LASTDRIVE" setting should be "H" or later. If there is no "LASTDRIVE" entry, scroll to the top of the window and enter "LASTDRIVE=x".

• 7

  Press the "Alt" and "F" keys simultaneously to exit the window, and choose "Yes" to save the settings, then reboot your computer to apply the changes.