How to change drives in MS-DOS and Windows command line

Updated: 07/13/2023 by Computer Hope
C: prompt

To change the drive letter in MS-DOS, type the drive letter followed by a colon. For example, if you wanted to switch to the floppy disk drive, you would type a: at the prompt. Below is a listing of common drive letters and their corresponding devices.


A partition is also treated as a drive, which means if you have a hard drive with two partitions, it's the C: and D: drive letters.

A: drive

Floppy disk drive (commonly the 3.5" floppy drive).

B: drive

A second floppy disk drive, if present (commonly the 5.25" floppy drive).

C: drive

Computer hard drive primary partition (unless the hard drive is not available or is bad). If your CD-ROM (compact disc read-only memory) is the C: drive, your computer is not detecting the hard drive.

D: drive

Commonly the CD-ROM drive or another drive unless the computer hard drive has multiple partitions. If multiple partitions exist, your CD-ROM drive is the last letter. For example, if one extended partition exists, your CD-ROM drive will be the E: drive because the hard drive partitions would use C: and D: drive letters.

Accessing a USB drive

To access a USB thumb drive or external drive, you must know what drive letter the computer has assigned to the drive. For example, if the USB (universal serial bus) is assigned to the F: drive, you can type f: at the prompt to switch to the F: drive.

What happens after switching drives?

After pressing Enter, your computer should change the MS-DOS prompt to reflect the new drive letter. If the drive does not exist, you will receive an error similar to the error below.

The system cannot find the drive specified.

If this occurs and you know the drive exists, it's likely the drive is having problems.

If the drive and drive letter do exist, but there is no media to read, then you'll get the below error.

The device is not ready.

For example, the error above will be received if you switch the drive with no floppy disk or CD (compact disc) inside.


To list the files on an alternate drive, you can also type dir followed by the drive letter. For example, "dir a:" lists the files on the floppy drive but will not switch your prompt to the floppy drive.