How to increase or decrease the size of the “C” drive in Windows

Some users, when working on a computer, are faced with the need to increase the size of the “C” drive in order to add additional space to the system partition. On the C: drive, by default, the Windows operating system, various system components, third-party programs are installed, user data is stored here.

In other cases, on the contrary, you need to reduce the “C:” drive if it is large in order to attach more space to the disk under the letter “D:” (or a disk under a different letter) that stores data.

There are several ways to solve this problem. In this guide, we will look at instructions on how to change the disk size in the Windows operating system, redistribute space between partitions with the built-in system tool, increasing or decreasing the size of the system disk.

First, let’s look at some of the reasons why this operation may be needed.

Choosing a partition size for the system drive

In most cases, the hard drive (hard drive) has one or two partitions that are displayed in the Windows file manager – Explorer. Some users create several additional partitions on the disk because it is more convenient for them to work on the computer.

In addition to the partitions displayed in Explorer, there are service partitions on the computer that are necessary to boot or restore the operating system. Service partitions are not in Explorer, they are displayed in the Disk Management snap-in.

On laptops, there is often an additional “Recovery” section that serves to restore the computer to the state at the time of purchase of the product. This section can be displayed in Explorer, or, conversely, be hidden.

Usually, users create partitions on the hard drive when installing Windows, or after buying a computer, because the laptop has one logical drive – “C:”. The operating system is installed on this disk and all other user data is stored: documents, music, videos, photos, etc.

If there is one disk on the PC, the user is recommended to create an additional partition to store user data. In the event of problems on the computer, you may need to reinstall Windows, which will result in the loss of all files located on the system drive.

If another disk partition (not the system partition) was used to store data, user data will be saved after reinstalling the operating system. Therefore, a significant part of users create an additional partition on the hard drive that acts as a data store on the computer.

Most often, redistribution of space is required in a more optimal way between the “C:” and “D:” drives. On your computer, instead of the “D:” drive, another drive may have a different drive letter. For example, a laptop has an optical DVD-ROM drive, labeled “D:” in Explorer, so another newly created hard drive partition will default to the next letter in the English alphabet. The user can change the drive letter by assigning any other free letter.

Most often, you need to change the size of the Windows drive, usually the “C:” drive where the operating system is installed. It is much less common to reduce the size of the “C:” drive if the user does not have enough disk space on the “D:” drive.

A small system partition quickly fills up with data; for optimal operation of the operating system, free disk space is required in the amount of at least 10-15% of the total volume of the disk (hard disk partition). Due to lack of space, Windows starts to slow down or work with errors. Installed programs also require free space to work, so it will be optimal to have about 20% of the system partition space unoccupied.

When redistributing space between partitions using a system tool, data will be lost on the disk used to store files due to the nature of the allocation of space on the hard disk. In order to change the disk size without losing data, you need to use third-party programs.

How to change the disk size in Windows when installing the operating system

Boot your computer from bootable media: flash drive or DVD. In Windows Setup, go to the window that asks where you want to install the operating system.

The user may have several options for further actions:

  • If you are reinstalling Windows and there is another disk or several data disks on your computer, you must first remember or write down on paper the size of the disk (disk partition) in order not to delete this partition when selecting or creating a disk for installing the system.
  • If the PC has one disk, delete all partitions left from the previous operating system: select the partition, and then click on the “Delete” button. Unallocated space will appear in place of deleted partitions.
  • If an operating system has not yet been installed on the computer, all available hard disk space is taken up by unallocated space.

In the example in this article, there are no other data disks on the PC, all partitions have been deleted. If your computer has a data partition, do not touch this drive.

First you need to create a system partition to install the Windows operating system:

  1. Highlight “Unallocated space on disk 0”.
  2. Click on the “Create” button.
  3. In the “Size” field, select the appropriate amount of space for the system drive. Leave some space to create another partition that will serve as data storage.
  4. Click on the “Apply” button.
  5. A warning window will inform you that additional partitions for system files will be created. Click on the “OK” button.
  6. In the next window, new partitions will appear on the hard drive: “Main”, on which you can install Windows and the “System Reserved” partition. This option is displayed when using an older BIOS.

Modern UEFI computers will have not one, but several small system partitions that do not need to be touched after they are created.

  1. Highlight the unallocated space, click on the “Create” button, and then “Apply” to create a new partition.
  2. Highlight the newly created partition, click on the “Format” button to format the partition to the NTFS file system. This operation can be performed after the system is installed from the Disk Management snap-in.
  3. The necessary partitions on the hard disk have been created. Select the partition selected for installing Windows (in the image – “Disk 0 Partition 2”), click on the “Next” button to continue installing the operating system on the computer.

How to increase the size of the “C” drive using Windows

The Windows operating system has a built-in disk management tool where you can create, expand, shrink, or delete a volume (disk).

We need to increase the system partition using the “D:” drive.

Keep in mind that increasing the “C:” partition by borrowing additional space from the drive under the letter “D” will not work without deleting information from the “D:” drive. After shrinking the disk, there will be unallocated space located after the “D” drive, which cannot be attached to the “C” drive due to the fact that the volume expansion function will not work. This feature works if the space to be attached is just behind the disk (“on the right”) to which the additional disk space is to be added.

Do the following:

  1. Press the “Win” + “R” keys.
  2. In the “Run” window, enter the command: “diskmgmt.msc” (without quotes), click on the “OK” button.
  3. The Disk Management window will open, displaying all the drives connected to the computer.

On this computer, the hard drive has two hidden system partitions (they have no letters) and two logical drives: “C:” and “D:”.

In order to increase the space on the “C” drive, we need to follow these steps:

  1. Delete drive “D”.
  2. Attach to drive “C” a certain size from unallocated space.
  3. Create drive “D” from unallocated space.
Before deleting a partition, copy the necessary data from the “D:” drive to a USB flash drive or external hard drive.
  1. Right-click on the “D:” drive, select “Delete volume …” in the context menu, agree to delete the partition.
  2. An area with unallocated space will appear on the computer’s hard drive.
  3. Right-click on the “C:” drive, select “Extend volume …” from the menu that opens.
  4. In the Extend Volume Wizard window, click the Next button.
  5. In the “Select disks” window, select the required amount of attached space, displayed in MB (megabytes).
  6. In the Completing the Extend Volume Wizard window, click the Finish button.

In the Disk Management snap-in, you will see that the size of the C: drive has increased. There is unallocated space left on the hard drive, from which we will create a new logical drive.

Now we need to re-create the “D:” drive:

  1. Right-click on the area of ​​the hard drive that says: “Unallocated”, select “Create a simple volume …”.
  2. In the New Simple Volume Wizard window, click the Next button.
  3. In the “Specify volume size” window, click the “Next” button. By default, the system tool will select all available unallocated space.
  4. In the “Format Partition” window, agree with the selected settings. You can set the volume label (the name under which the disk will be displayed in Explorer): “New volume” (default), “Local disk” or any other name. In this example, I have chosen the “vellisa” label.
  5. In the Completing the Create Volume Wizard window, click Finish.

As a result, a new drive “D:” appeared on the computer.

How to reduce disk size using Windows

Now consider the reverse situation, where you want to shrink the “C:” drive by adding some space to the drive under the “D:” letter (or to a drive with a different letter).

Go through the following steps:

  1. Right-click on the “C” drive, select “Compress volume …” from the context menu.
  2. The Shrink Space Query window polls the volume to estimate available space.
  3. The window that opens shows the amount of disk space available for compression. If the available size is large enough, you can choose a smaller size for compression. Click on the “Compress” button.

Unallocated space appeared between the C: and D: drives in Disk Management.

Attaching this space to the “D” drive will not work, because it is located “to the left” of the “D” drive. If this location were “to the right” of the “D:” drive, we could expand this partition without removing the “D” drive.

Delete the “D:” drive, and then create a new partition under the letter “D:” in place of the unallocated space. This process is described in detail above in the article.

Article Conclusions

To increase the size of the “C” drive on which the Windows operating system is installed, you need to reallocate space from another hard disk partition. You can perform this operation using the system tool. Some of the disk space will be taken from the “D” drive (or a drive under another letter) and then added to the “C” drive.

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