How to Use the D Drive When the C Drive Is Full?

How to use the D drive when the C drive is full? In this post, you’ll not only learn to fix the issue of insufficient space on the C drive but also learn to fully make use of the D drive.


By Michael / Updated on May 12, 2023

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My C drive is full but D drive empty

"My C drive (29.2GB) is low on space…I have QuickBooks and Peachtree programs on it that I cannot get rid of. They won’t uninstall. I’ve even moved files to the D drive but It wasn’t enough. Want to do a system restore but there’s not enough space. I have an empty D drive (418GB). What should I do?"

Why’s the C drive full and what will happen?

C drive, usually the boot drive, is where your system-related files along with personal files like photos and video are stored. The C drive is critical for the normal performance of your computer but sometimes, it can be lacking in storage space. When the C drive is full, the Windows system becomes sluggish and less responsive and you may encounter constant crashes and errors as well.

Then, why does the C drive become full?

low disk space

As mentioned above, the C drive holds indispensable system-related files and personal files. However, over time, the C drive could have less storage space left as people install more and more third-party software to it. Meanwhile, other files could be added to the drive for different reasons. For example, after upgrading one Windows version to another, a Windows .old folder will be generated that occupies at most 20GB of storage space.

How to use the D drive when the C drive is full?

When you find the C drive is full, don’t panic. Then, what to do next is checking whether there’s enough storage space on the D drive. If the answer is yes, it’s your lucky day as there’re some tricks you can try with the D drive’s space.

Option 1. Extend the C drive after deleting the D drive

Windows has its strong built-in utility Disk Management to perform various operations including volume deletion, extension, and disk format. Many people tend to shrink the D drive to create unallocated space and use it to extend the C drive.

However, the unallocated space is always right behind the drive you shrink while a drive can be extended only when the unallocated space is right next to it. Namely, if you shrink the D drive, the unallocated space will lie right next to it but you cannot extend the C drive with it as there’s the D drive in the way. In this case, the option "Extend Volume" will be greyed out.

cannot extend

But there’s still a workaround as you can delete the entire D drive to create a piece of large unallocated space right next to the C drive for extension if the C drive is full but D drive empty.

1. Right-click on "This PC > Manage > Storage > Disk Management". Then, right-click on the D drive and choose "Delete Volume".

delete volume

2. After the deletion, you’ll see the D drive has turned into unallocated space. Now, right-click on the C drive and select "Extend Volume".


3. Follow the onscreen guide and hit "Next" all the way until the last step. Hit the "Finish" button to complete the process.


Look into Disk Management or File Explorer to check whether the C drive has become larger.

Option 2. Allocate some free space to the C drive from the D drive

If the D drive is not empty, deleting it can cause severe data loss. In this case, you can try allocating some free space from the D drive to the C drive without deleting any necessary files. To get it done securely, here, I recommend AOMEI Partition Assistant Professional – a multifunctional and efficient disk manager.

Download the demo of this powerful software to have a try!

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Step 1. Install and launch AOMEI Partition Assistant Professional, right-click on the D drive and select "Allocate Free Space".


Step 2. In the next window, preset the amount of free space to allocate and choose the C drive as the destination.

d to c

Step 3. Click on "Apply" to commit the operation.


Option 3. Move apps from the C drive to the D drive.

If the C drive full issue is caused by too many large apps, you might as well move them to the D drive to free up enough space. Luckily, the AOMEI product contains the latest developed "app mover" to help transfer any apps and programs including Microsoft Office and video games from one drive to another without data loss.

Step 1. Run the AOEMI product. Click “Free up” on in the top toolbar, and choose “App Mover”.

app mover

Step 2. Select the C drive and hit "Next".


Step 3. Tick the apps you want to move and choose the D drive as the destination. After that, click on "Move".


Step 4. Hit "OK" to confirm the operation and the app transfer will start.


Step 5. After completed, click on "Finish".


How to use the D drive when the C drive is full? You can try both Windows built-in Disk Management and a third-party disk manager AOEMI Partition Assistant Professional. With the former one, you can delete the entire D drive and use the generated unallocated space to extend the C drive. But not everyone is willing to delete the D drive and thus, the AOMEI product becomes the best choice. With it, you can not only allocate free space from the D drive to the C drive but also, move large apps from the C drive to the D drive to free up disk space. There’re also many other useful features included by this software such as partition merging, hard disk clone, and OS to SSD migration. If you want to use this tool on Servers, you can try the Server edition.

Michael · Staff Editor
Michael is a professinal editor of AOMEI editor team.