By Emily / Last Updated September 24, 2021

What happens when C: drive is full?

Many Windows users have this problem: “My C: drive is full without reason”. You may also receive a Low disk space warning. When the system drive is in low disk space, some programs may not work properly. What’s worse, it may result in a system crash. Therefore, you need to fix this problem as soon as possible.

Why is C: drive full?

▪ Viruses and malware may keep generating files to fill your system drive.

▪ You may have saved large files to C: drive that you are not aware of. For example, the default download folder is located in C: drive.

▪ Pages files, previous Windows installation, temporary files, and other system files may have taken up the space of your system partition.

There might be more reasons behind C: drive mysteriously full. You can use one or more of the methods below to clean up C: drive space in Windows 11/10/8/7.

Solutions to C: drive full without reasons Windows 11, 10, 8, 7

Having realized the reasons for the "my C drive is full" issue, it's time to learn how to fix it.

Solution 1. Scan your computer for software or virus

When you notice C: drive is full, you should first do a virus scan before wondering what you can delete. You should have good anti-virus software installed. At least, you should have Windows Defender and update it to the latest version. Then you should start to run a clear scan. To protect your computer against viruses and malware, you should make sure your system is up to date.

Solution 2. Run Disk Cleanup

Disk Cleanup is a Windows built-in tool that allows you to delete some files that you cannot delete in Windows File Explorer.

Step 1. Right-click on C: drive and select Properties, and then click "Disk Cleanup" button in the disk properties window.

Step 2. In Disk Cleanup window, select the files you want to delete and click OK. If this does not free up much space, you can click Clean up system files button to delete system files. From there, you are able to delete previous Windows installation (Windows.old folder), system restore points, Recycle Bin, and other system files.

C Drive Cleanup

Solution 3. Delete hibernate file

Windows reserves about half of the RAM space for the hibernation file. If your computer RAM is 8GB, the hibernation file (hiberfil.sys) is about 4GB in size.

To delete the hiberfil.sys file:

1. Go to Start menu, type “cmd” and right click on the results Command Prompt and select Run as administrator.

2. Then type “powercfg.exe -h off” and press Enter.

After that, you should see a few more gigabytes of free space on system drive.

Solution 4. Uninstall some programs

Windows has many built-in programs, especially in Windows 10. Some of them, you may never use. Then you can uninstall the programs that you do not actually need. Also, you may have installed programs that won’t be needed in the future. Uninstall them to free up space.

You can click (right-click in Windows 10) the Start button, then Control Panel >Programs > Programs and Features.

In Windows 8/8.1, you can type “uninstall” and then select Programs and Features from the results.

From there, you can right-click on the program you want to uninstall and select Uninstall.

Solution 5. Extend system partition without data loss

If after all these steps, your C: drive is still full, you may consider adding some space to system partition from another partition on the same hard drive.

You can use free partition manager software AOMEI Partition Assistant Standard to extend C: drive without the need to delete the partition behind it.

To extend system partition in Windows 11/10/8/7:

1. Download this free partition tool and run it.

Download Freeware Win 11/10/8.1/8/7/XP
Secure Download

2. Right click on a partition that has more free space and select “Resize Partition". If your hard drive has some unallocated space, you can skip this step and jump to Step 4.

Resize Partition E

3. In a pop-up window, drag the partition’s end leftwards to shrink this partition to generate some unallocated space.

Drag to Right Side E

4. Right-click on the C: drive and select “Merge Partition”. In the next screen, check C: drive and the unallocated space, and then click “OK”.

Merge C and Unallocated Space

5. Click “Apply” to save these changes.

Apply Merge C and Unallocated Space

Solution 6. Transfer some big apps from C drive to another drive

If the C drive has contained many big programs or applications, you can try to move some of them to another bigger partition to free up space on C drive and solve the C drive full issue in Windows 11,10, 8, 7. For this task, you can upgrade the AOMEI Partition Assistant Standard to Professional edition. It develops the "App Mover" function that allows you to move apps from one drive to another. You can download the demo version and have a try.

Step 1. Install and launch AOMEI Partition Assistant Professional. Click "All Tools" > "App Mover".

App Mover

Step 2. Click C drive and hit on "Next".

Select Partition

Step 3. All movable apps in C drive will be listed, choose whichever you need to move, select the destination path and click on "Move".

Tick Apps

Step 4. In the pop-out window, click "OK" to close the running applications and start moving app.


Those methods are all effective for solving C drive full without reason in Windows 11, 10, 8, 7. Another bonus solution to my C: drive is full without reason is to upgrade to a larger hard drive. You can clone the old hard drive a new one or SSD (solid-state drive) without reinstalling Windows.