How to Use Unallocated Drive Space in Windows - dummies

How to Use Unallocated Drive Space in Windows

By Dan Gookin

To make the unallocated portion of a hard drive useful, you must create a new volume, one that’s recognized by Windows. You can create three types of volumes:

Simple: This typical hard drive is the type that most PC users have in Windows. If you’re shrinking a volume to create a new logical drive, such as a new drive F (or something), this option is the one you want.

Spanned: A spanned volume combines two or more unallocated volumes, even on separate physical hard drives, creating a new drive. The new drive combines all the space of the various unallocated volumes into a single volume.

Striped: Striped volumes are used to improve disk performance by spreading information between multiple disks. The net result is that several drives are used to quickly access information, which makes all disk operations faster. You need two or more unallocated chunks of disk space to set up a striped volume.

If you’re using the new volume to install another operating system on the PC, do not create another volume in Windows. Just leave the volume unallocated and let the other operating system’s installation program do its thing with the drive.


  1. Open the Disk Management console.

    1. Open the Control Panel.

    2. Open the Administrative Tools window.



      In Windows XP, open the Administrative Tools icon.

    3. Open the Computer Management icon.

      In Vista, click Continue or type the administrator’s password.


    4. Choose Disk Management.

  2. Right-click the unallocated volume.

  3. Choose New Simple Volume from the shortcut menu.

    The New Simple Volume Wizard appears.

  4. Click the Next button.


    The size is already preset to equal the entire disk capacity, which is recommended. If you need to set it to a smaller size, do so. The remaining space on the drive continues to be unallocated.

  6. Click the Next button.

    Windows lets you assign the drive a letter, or you can mount the drive on an NTFS volume as a folder. Or, you can do neither, depending on how you fill in the wizard.

  7. (Optional) Choose a letter for the new volume.

    My advice is to use the letter that’s provided.

  8. Click the Next button.

  9. Ensure the option Format This Volume with the Following Settings is chosen.

  10. Ensure that the NTFS format is chosen.

  11. Click the Next button.

  12. Click the Finish button to create the new volume.

    Windows prepares the disk by formatting it, laying down the tracks (or parking spaces) for the files. The amount of time taken to complete the operation depends on the size of the volume. Larger disk drives take longer to format.


  13. When the operation is complete, you can close the Disk Management console.


The new volume may have less capacity than anticipated. The missing bytes are overhead, used by the formatting process.