This document applies to HP and Compaq PCs with Windows 7.
Understanding drives, partitions, and volumes
A partition is an area of a hard disk that can be formatted and assigned a drive letter. On a hard disk, a volume is a formatted primary partition or logical drive. The terms partition
and volume
are often used interchangeably.
HP and Compaq computers with Windows 7 have hard disk drives that contain at least two partitions: the main partition for Windows and your work, and a recovery partition to restore the computer back the way it came from the factory. Here is a list of some of the partitions you may find on your hard drive:
- The main partition, usually labeled with the letter C, contains the system files, program files, and usable file storage space.
- A recovery partition, usually drive letter D and labeled RECOVERY, contains system recovery information in case the files on the C partition are damaged or unusable.
- A hidden partition may exist called SYSTEM. A SYSTEM partition is used by Windows to store protected files for troubleshooting and should not be altered.
- Your computer may also have a partition called "HP_TOOLS". If so, this partition contains HP tools for UEFI that you can use to help troubleshoot boot problems or test for hardware failures.

CAUTION:When using the steps in this document, do not
delete the SYSTEM, Recovery or FACTORY_IMAGE partition or use it for file storage. Doing so may prevent boot troubleshooting or recovery in the event your computer encounters a major problem.
Adding a new drive letter
Add a new drive letter to the computer using one of the following methods:
- Install an additional hard drive - If you need more space for photos, videos, music, or other files, add a new hard disk drive or USB storage device. An additional hard disk can be inside the computer (internal) or external, attached to a USB connector on the computer. When you add a new storage device, Windows automatically assigns a new letter.
NOTE:To add an internal hard drive, the computer must have an empty drive bay. Most mid tower or larger desktop PCs have space for one or more additional hard drives. Almost all notebooks, Slimline, and AiO computers do not have space for an internal drive. - Partition the existing drive - If you do not need more file storage space but would like to view another drive in Windows, create another partition on the existing hard disk. This might be useful if you need to share files on a drive but want to prevent access to your personal files by keeping them on another drive.This method does not add more space, but re-allocates some of the empty space on the existing hard disk into another partition. This space is then treated as another drive and labeled with its own drive letter.
Creating a new partition
To create more partitions or volumes, the hard disk must contain unallocated space that is not part of an existing partition. Shrink the volume on an existing drive to create unallocated space and then create and format a hard disk partition.
Read the following section for more detailed instructions. If the heading has a plus (+) sign, click it to expand the information.
- To open the Disk Management tool, click StartOpening the Disk Management toolOpening the Disk Management tool
. In the Search field, type partition
. Then click Create and format hard disk partitions
.The Disk Management tool opens and displays information about the data storage devices on the computer. - To create unallocated space on the drive, right-click the drive you want to partition. For most applications, select the C: drive.Then click Shrink Volume...
CAUTION:Do not use the Recovery or FACTORY_IMAGE partition to create a new partition. Doing so might prevent the HP Recovery Manager from recovering the computer when the information on the C: partition is damaged. - Do not make any adjustments to the settings In the Shrink window. Click Shrink .When the Shrink is complete, the new partition displays in the Disk Management utility as Unallocated space.
- Right-click the new partition. In the menu that displays, click New Simple Volume.. .
- The New Simple Volume Wizard displays. To continue, click Next .
- The Specify Volume Size window displays. Type in the volume size, or click Next to accept the default setting.
- The Assign Drive Letter or Path window displays. Select a drive letter and click Next .
- The Format Partition window displays. To name the drive, type a name in the Volume label box. Then click Next .
NOTE:Do not select Perform a quick format or Enable file and folder compression . - The settings window displays. Click Finish .
- The Disk Management utility displays showing the formatting progress.Figure 10: Formatting the new partition
When the format is complete, the new drive shows in the Disk Management utility.If the AutoPlay window displays, click the X in the upper-right corner to close it.
Changing a drive letter
To change the drive letter, you can assign the letters C through Z to each drive on the computer. The system partition is usually labeled with the letter C while the letters A and B are reserved for floppy disk drives or removable drives. If the computer does not have floppy disk drives, you can assign A and B to volumes.

NOTE:Some MS‑DOS and Windows programs make references to specific drive letters. If you change a drive letter, some programs that you have installed on your hard disk might not work correctly.
You cannot change a drive letter if the drive is either a system partition or a boot partition. If you get an error, the partition or drive you are trying to change might be in use. Close any program or window that is using the partition or drive and try again.
Complete the following steps to change a drive letter.
- To open the Disk Management tool, click StartOpening the Disk Management toolOpening the Disk Management tool
. In the Search field, type partition
. Then click Create and format hard disk partitions
.The Disk Management tool opens and displays information about the data storage devices on the computer. - Right-click the partition or drive you want to rename and then click Change Drive Letter and Paths...Figure 13: Changing a drive letter

- In the menu, select the new drive letter. Then click OK .
- The Disk Management caution message is displayed. Click Yes to continue.
Removing a drive letter
A drive letter can be deleted by using the Disk Management tool.

CAUTION:Deleting a volume erases all the data on it. Back up any data you want to keep before deleting.
- On the drive you want to delete, back up any data you want to keep.
- To open the Disk Management tool, click Start
. In the Search field, type partition
. Then click Create and format hard disk partitions
.The Disk Management tool opens and displays information about the data storage devices on the computer. - Right-click the drive letter you want to remove. Then click Change Drive Letter and Paths...
- In the Change Drive Letter window, click Remove .
- The Disk Management caution message displays. Click Yes to continue.The drive letter disappears. To use this hard drive space again, continue to the next section to remove the partition.
Removing a partition
From the Computer Management window, delete the volume, delete the partition, and then add the unallocated space to another disk.
Read the following section for more detailed instructions.
- Right-click the volume or partition you want to delete, and then click Delete Volume...
- If you have backed up the data you want to keep, click Yes .The drive letter disappears and the partition is labeled as Free space.
- Right-click the free space. In the menu that displays, click Delete Partition...Now the space is shown as Unallocated .
- Right-click the drive to which you want to add the unallocated space. In the menu that displays, click Extend Volume...
- The unallocated space can now be used.
Related support
Microsoft support article -
What are system partitions and boot partitions?
(in English)
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