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The Best Windows Disk Management Guide for Beginners

inside a hard drive

Nowadays, OEM manufacturers do not partition computers when they leave the factory. Besides the widespread adoption of SSDs, which has weakened the concept of “installing the system on the C drive and other software and data on other drives”, OEM manufacturers have learned to simplify-minimizing pre-installed software to present the purest system to users, allowing them to decide how to use it.

Not everyone buys a computer just to watch movies or play games; many users need to write documents and design, and they have certain requirements for data security. This determines that there is still a huge market demand for hard disk partitioning.

The Windows system comes with a powerful built-in tool–Disk Management. Below, I will simulate daily needs and demonstrate how to create, merge partitions, assign and modify drive letters.

I. Creating a New Partition

This is a common need for computer users. A few years ago, when the price of SSDs was still high, high-end computers generally used a combination of SSDs and HDDs. In such combinations, a 128GB or 256GB SSD was usually used as the system drive, and the HDD was used as the data drive. However, with the continuous decline in SSD prices, 1TB and 2TB solid-state drives are becoming more common, and the demand for partitioning has also increased.

In this example, I plan to divide Disk 0 into three partitions( except EFI System Partition and Recovery Partition ). From the following image, you can see that Disk 0 currently has only one operational partition, which is C drive. Therefore, I first need to compress some space out of C drive.

Windows partitions

Right-click on C drive and select “Shrink Volume”.

Shrink Volume in Windows Disk Management

In the “Enter the amount of space to shrink in MB” text box, enter the capacity planned to be compressed for other partitions. The unit is MB, 1GB = 1024MB. The compression value should be less than the “Available shrink space size” because the premise of compression is not to affect the existing data in the original partition.

Shrink Volume in Windows Disk Management

Click “Shrink” and you can see an unallocated space on the right side of D drive. This space is not yet a partition. If you want to store and read data in it, you must create it into a new partition.

Unallocated space in Windows Disk Management

Right-click on the unallocated space and select “New Simple Volume,” then enter the size of the new partition. The current available capacity is 20GB. Suppose I want to create two new partitions of 10GB each; then I must enter 10240 in the first operation, the unit is MB.

Create a new Simple Volume in Disk Management
Create a new Simple Volume in Disk Management

Click Next, assign a drive letter, and then format the partition for system use. It is recommended to use the default NTFS format for the disk, as this is within the Windows system.

assign drive letter in Disk Management
format partition in Disk Management

Complete the process, and Disk 0 will look like the image below. One partition has been created(D drive), and there is still 10GB of unallocated space.

Windows partitions with unallocated space

Repeat the above steps to create another partition(E drive).

Winidows partitions with drive letters

II. Merging Partitions

Many times, we find that the actual usage of each partition is different from what we expected. Some disks are full, while others are still empty. At this time, we need to merge two partitions together or allocate part of the space of one partition to another.

Note: This operation involves data security, so please consider thoroughly and back up your data before proceeding.

Before operating, you must understand this rule: you can only merge partitions from right to left, and only adjacent partitions can be merged. Because partitions are just a concept imposed by the system on the disk. No matter how many partitions are divided, they are all on a complete piece of disk, and there are no physical boundaries. The system records the starting point of a partition and determines the size of the partition by adjusting the end point position. The end point position can be changed, but the starting point position cannot be changed once it is determined, unless the partition is deleted, and the starting point position will be cleared.

In the part of creating a new partition, when we compressed C drive, the unallocated space that was compressed out was on the right side, not the left, because of this rule.

Assume the following partitions:

Winidows partitions with drive letters

Assuming I want to merge the capacity of partition E into D drive, I can operate like this:

First step, delete partition E. All data in E drive will be deleted, and the space originally occupied by E drive will become unallocated space.

Delete Volume in Windows Disk Management
Windows partitions with unallocated space

Second step, merge the unallocated space into the left partition, that is, D drive. Can C drive get this part of the space? No, because of the rules mentioned above, only adjacent spaces can be merged.

Right-click on D drive and select “Extend Volume,” then enter the size you need to expand.

Extend Volume in Disk Management
Extend Volume in Disk Management
Windows partitions in Disk Management

From the above operations, it can be seen that when expanding a partition, you can only add unallocated space to an existing partition, and existing partitions cannot be directly added to the adjacent partition on the left.

Assuming I have C drive and D drive, and currently, C drive space is insufficient while D drive is still idle. How can I allocate some D drive space to C drive without deleting D drive data?

There is a workaround:

  1. Compress D drive, and the amount of compression space should be greater than the space D drive has used currently;
  2. Create the compressed space as E drive;
  3. Copy all D drive data to E drive;
  4. Delete D drive and merge it into C drive, at this point, the system only has C and E drives left;
  5. Modify E drive to D drive according to the method below.

The principle of this scheme is that the Windows system finds files through disk paths, so as long as the file directory does not change during the copy, changing E to D, the path is exactly the same as before, and the program can still run. Therefore, we only need to create an unallocated space directly to the right of C drive, but the premise is that the space planned for D drive is greater than the space D drive has used currently.

III. Assigning and Modifying Drive Letters

When creating a new partition, we saw a step where we assigned a drive letter, such as the most common C, D, E, F… in Windows Explorer.

The system determines the path through the drive letter, which means that partitions without a drive letter cannot be used directly in the system and will not be displayed in Explorer. From the Disk Management interface, you can see that some partitions do not have a drive letter, they are EFI partitions, recovery partitions, or partitions established by OEM manufacturers for specific functions – the most common is the factory system restore function, such as Dell’s SupportAssist OS Recovery.

Note: Changing or deleting the drive letter will make the programs in the partition unusable because the system cannot find the path.

In Disk Management, right-click on the partition that needs to add, modify, or delete a drive letter, and select “Change Drive Letter and Paths…”:

Change Drive Letter and Paths in Windows Disk Management
change drive letter and path

Select the partition and operate through the buttons below.

  • Add: Add a drive letter to the partition that has not been assigned a drive letter. If there is already a drive letter, it cannot be added again;
  • Change: Replace the current drive letter with an unoccupied drive letter;
  • Remove: Clear the current drive letter, making the partition a state without a drive letter.

The system will automatically detect used and unused drive letters. Suppose I want to exchange the drive letters of D and E partitions, then I need to change one of the partitions to a drive letter other than D and E first, that is, introduce a “temporary variable.” Replacement process:

  • D -> G
  • E -> D
  • G -> E

The above is the method and example of using the system’s built-in Disk Management function for partition management. There is basically no need to use third-party partition tools. Third-party tools such as Partition Magic, AOMEI Partition Assistant, etc., are actually calling system interfaces to manage disks. They can achieve cross-partition space allocation and other functions, but these operations may lead to partition table damage, data loss, and system instability. Therefore, if it is just a simple partition requirement, it is best to complete it with the method introduced in this article.

If you have any questions, please discuss with us in the comment section. If this article is helpful to you, please share it with your friends or forward it on social media. Thank you very much for your reading and support.


A skilled Windows user and explorer. Mainly focus on Tips and Fixes.

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