By Dylan / Last Updated February 23, 2021


My drive C is low on space

My C: drive (29.2 GB) is low on space. There is not enough space in my C drive to download new programs. And I found my D drive is empty. Thus, I shrink D drive to get an unallocated space. But when I try to extend C drive with it, the option Extend Volume greyed out. How can I extend my C drive?”

C drive is easier to get full for different reasons, such as unreasonable partition size allocation, installing too many programs. C drive is where the operating system installed, so generally, C drive needs to be allocated with enough space and we should not install other third-party programs in it. Otherwise, your C drive will be getting full quickly, and your system will run slowly.

C drive full and D drive totally empty-What to do?

So some people may use Disk Management to shrink D drive to get an unallocated space and extend C drive with it. However, the unallocated space you add to the C drive must be adjacent and behind the C drive. That is why the option Extend Volume greyed out. Then, what should you do?

Extend C Volume Grey Out

If the D drive is totally empty without a file saved, you can directlydelete it to get contiguous unallocated space behind the C drive. Refer to the following part, and learn how to delete D drive and extend C drive.

Warning: D drive has to be adjacent to and behind C drive, otherwise Disk Management does not allows you to extend C drive with the deleted D drive.

1. Right-click computer> Manage > Storage > Disk Management. And the current partitions will be presented on the window. Right-click partition D and choose "Delete Volume".

Delete Volume

2. Click "Yes" to execute, and all data and files on the D drive will be deleted.


Warning: If the partition D has some files and it is currently used, you will be informed this. You can click "Yes" to force the deletion of Partition D. But it might cause unexpected errors, please be cautious.

3. When the process finishes, you can see the space of D volume becomes an unallocated space.Right-click on C drive, and choose "Extend Volume".


4. “Extend Volume Wizard” will pop up, follow the prompts and click “Next

Extend Volume Wizard

5. In this window, select the disk(s) from which we want to get free space. And you can specify how much free space adds into the C drive. And click "Next".

Extend Volume Wizard Select Disks

6. Check the setting. And click "Finish". When the process is completed, your C drive will be extended, and D will be deleted.


What if C drive full, D drive almost empty?

If there is no data on D drive, you can delete it to get an adjacent unallocated space and extend C drive with it. What if your D drive has plenty of space while still has some necessary data?

In such a condition, you can turn to AOMEI Partition Assistant Professional, its "Allocate Free Space" function allows you to allocate unused or free space from D drive to C drive without deleting. You can download the demo version to see how it works:

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

Step 1. Install and open AOMEI Partition Assistant Professional. The condition of the disk will be displayed on the interface. Right-click the drive D or other partitions you want to allocate and choose "Allocate Free Space".

Allocate Free Space

Step 2. In the pop-up window, you could specify the free space to be allocated and choose which partition you want to extend.

Allocate From D To C

Step 3. Then click “Apply” to execute operation.

Apply Allocate Free Space


That is how you can deal with the problem that C drive is full D drive is empty in Windows 10, 8, 7. You can delete D drive and extend C drive with contiguous unallocated space within Disk Management. But when there are data that you don’t want to lose, AOMEI Partition Assistant is a nice choice.

In addition, AOMEI Partition Assistant also has other functions, such as migrate operating system to another drive, partition recovery, convert OS disk from MBR to GPT and so on. And there is AOMEI Partition Assistant Server version, if your PC are running with Server system, you can solve you problem with it.