3 Ways - Disk Management Can’t Extend Boot Partition in Windows

This article details the reason of Disk Management can’t extend C drive with unallocated space and tells how to fix “can’t extend boot partition” issue in Windows 7/10.


By Emily / Updated on May 12, 2023

Share this: instagram reddit

Can't extend boot partition in Disk Management

Hello, all. This question bothers me for a long time. So please help me figure it out. Here is the case: I have 80 GB in system boot partition C which becomes red in Explorer a few weeks ago. I’ve received “low disk space” warning several times. When I go to Disk Management , I found that I have some unallocated space at the end of the disk. I guess I could extend the C drive with that unallocated space. However, when right-click my boot partition, only to find that the “Extend Volume” is grayed out. How come? I was told to delete partitions in the middle of the disk to complete extending. This is horrible since I’ve installed many applications in D drive. Why can’t Windows just see the unallocated space and move it to my C drive?”

Low Disk Space Warning

The above situation may not be unfamiliar to most Windows users. There are many cases that need to extend boot partition Windows 10. Nevertheless, issues like “Disk Management can’t extend boot partition” always prevent us from managing computer better. What are the exact factors that affect our operations?

Why can’t extend boot partition in Windows 10, 8, 7?

As a matter of fact, reasons could be very simple. When you can’t extend partition in Windows 10 or Windows 7, two main reasons account for Windows 7 or Windows 10 Extend Volume grayed out:

The unallocated space is not adjacent to the boot partition you want to extend. This is the same reason for the trouble in the example. You can only extend the boot partition into contiguous unallocated disk space.

◢◢There is no unallocated space on the same physical hard drive. Some users have two or more hard drives installed. But it is impossible to add unallocated space of this physical basic disk to a partition on that physical basic disk.

In Windows XP or the previous, you are likely to encounter “can’t extend C drive with unallocated space” trouble because there is no option named “Extend Volume” in Disk Management. "Extend Volume" and "Shrink Volume" are new features come with Windows 7 and later. Yet it supports to resize partition using Diskpart. The first case can be solved by using following methods, but the second one requires hard drive RAID or dynamic disk.

By the way, there is another situation that you cannot extend partition in Windows. If you have unallocated space on your USB drive, SD card or the like, when right click the first partition in Disk Management, the "Extend Volume" is also grayed out. Windows only recognizes the first partition on a removable device, so even if you have more than one partition on the device, that option is invalid.

Solved: Windows can't extend boot partition

Can you extend a boot partition? Of course! Now that Windows Disk Management cannot help you in extending system boot partition, it is time to seek help from third-party software. Many  partition managers on the market can solve this trouble, and AOMEI Partition Assistant Professional is one of them. This disk partition software allows you to resize partition, move partition, delete partition, etc. With the help of this partition tool, you can solve the aforementioned issue like a breeze. Windows 10, 8.1/8, 7, XP, and Vista are supported.  Install and run this software. You have three methods in total to choose.

Note: Please back up files that you care about most in case of data loss under inappropriate operations.

You can download its demo version to have a try!

Free Download Win 10/8.1/8/7/XP
Secure Download

Method 1: Extend Boot Partition by Moving Unallocated Space

1. Right-click the partition next to the unallocated space and then select “Resize/Move Partition”.

Move Partition

2. In the pop-up window, drag this partition to the right side.

move to the right side

3. You'll find the unallocated space is before this partition. Click “Apply” >“Proceed” to execute it.


4. Repeat the above steps until the unallocated space is adjacent to the boot partition.

Method 2: Extend Boot Partition by Merging Unallocated Space

1. Right-click the boot partition (C drive in general) and choose the “Resize/Move Partition” option.

Merge Partitions

2. In the pop-up window, check C drive and the unallocated space and then click “OK”.

Merge Unallocated Space

3. Click “Apply” > “Proceed”.

Method 3: Extend Boot Partition by Allocating Free Space from Existing Partitions

If there is no unallocated space on the same hard drive, this method will do you a big favor. It will allocate free space from other redundant partitions to the boot partition directly. The whole process can be completed in one step. 

1. Right-click the partition which has redundant space, and then click “Allocate Free Space”.

Allocate Free Space

2. In the pop-up window, specify the size of free space and choose the boot partition as the target partition.

Specify Free Space

3. Click “Apply” > “Proceed”.

AOMEI Partition Assistant Professional has many other useful features in computing. For example, you can migrate OS from GPT disk to GPT/MBR SSD or HDD; Convert system/boot disk between MBR and GPT styles; Convert Dynamic disk to basic and vice versa; and manage disk partition from Command Prompt.


Next time when you face "Disk Management can't extend boot partition" or similar troubles, I am sure you'll fix it confidently. In Disk Management, you may want to convert FAT32 to NTFS without formatting, which could be done using AOMEI Partition Assistant as well.

Emily · Staff Editor
Emily is an English editor of AOMEI Technology; she has a great passion for providing easy solutions for people to tackle with all disk or partition management problems. In addition to writing articles about disk/partition management, she also edits great tutorials on how to back up and restore disk for data security. In her spare time, she loves to learn computer skill to improve herself or stay with her family to enjoy a good day.