How to fix system C: drive out of space

by Jordan, Updated on: May 23, 2020

This article explains why system C drive runs out of space and how to fix this issue with ease.

Applies to: Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, Windows Server 2019, Windows Server 2016, Windows Server 2012 (R2), Small Business Server 2011, Windows Server 2008 (R2) and Windows Server 2003 (R2).

It is headache to most of Windows computer users when system C: drive is running out of space. Microsoft does not give helpful solution and only provides Disk Cleanup to help free up disk and reclaim space. Many people feedback that C drive runs out of disk space again shortly after cleaning up. In this article, I'll show you detailed steps to fix C drive out of space issue, they are valid for Windows 10/8/7/Vista/XP and Server 2019/2016/2012/2008/2003.

Why system C drive is running out of space

No matter you use Windows laptop, desktop or a server, you'll encounter the annoying issue. Comparing with data volume, system partition C is very likely running low on disk space. To a data volume, you can easily transfer files to other place, but to system C drive, it is a bit complicated.

C drive out of space

There are many types of junk files generated or saved to C drive continuously, for example, Temporary Setup Files, Downloaded Program Files, Temporary Internet Files, Recycle Bin, Cache, Logs.

In personal computer and Windows Server, you need to install many programs. The more you installed, the less free space left in C drive. Many server administrators know the importance to change default installation path, but many files are still saved to C drive.

Other large files such as system backup, restore point, Windows Updates can eat large amount of free space easily.

When system C drive is running out of space in Windows Server 2012/2008/2003 and Windows 7/Vista/XP, you'll receive the Low Disk Space warning on bottom right corner. In all Windows PC and Server, when C drive is getting full, it will be changed to red in File Explorer. In this situation, you begin to suffer from computer performance down. The less free space left in C drive, the higher risk of computer stuck, reboot unexpectedly or even crash. It is urgent and this is the reason why Microsoft create these warnings. You'd better try to fix C drive out of space issue as fast as possible.

How to fix C drive out of space issue on Windows PC and Server

When a data drive is getting full, you can simply transfer files to other place, but you cannot do this to system C drive. As I said in the beginning, Microsoft only provides Disk Cleanup to help free up disk space. To most of the servers and PCs, this utility can reclaim disk space more or less, but it cannot solve this problem completely. Even if you got over 10GB free space, it will be eaten up quickly. You'd better add more free space to C drive.

Step 1: Clean up disk to reclaim free space

Cleaning up disk cannot solve this problem completely, but it is still helpful. After getting some free space, your laptop/desktop/server could keep running in the right way. In addition, there's free space to install programs to help solve this problem.

To free up and reclaim disk space, you may either use Windows native Disk Cleanup or 3rd-party software. I always recommend Windows Disk Cleanup, because it is able to delete common junk and safe and unnecessary files fast and safely.

Follow the steps to enable Disk Cleanup on Windows Server 2008 and 2012, other versions are enabled by default.

How to fix C drive out of space issue with Windows built-in Disk Cleanup utility:

  1. Press Windows and R together on the keyboard.
  2. Type cleanmgr and press Enter.
  3. Select C: drive in the drop-down list and click OK, then Disk Cleanup dialog box will pop up.
  4. Click the check-boxes in front of the files that you want to remove, then click OK and confirm.

Disk Cleanup

If you want to reclaim more disk space, follow the steps to try additional methods in a specific OS:

Step 2: Add more free space to C drive

This step is dispensable especially to the computers that C drive are created small. It is similar with a smart phone, if you use a 16GB device, you have to clean up frequently. But if you use a 256GB device, you won't encounter this problem for a long time.

Disk partitions are allocated while installing Operating System or created by OEM manufacturer, but you can resize partition with without losing data. It is very easy to add more free space to C drive from other partitions. To do this, you just need to drag and drop on the disk map.

Download NIUBI Partition Editor and follow the steps in the video:

Video guide

This video is created on Windows 10, the steps are similar on other versions. Better than other tools, NIUBI has Virtual Mode, Cancel-at-will and 1-Second Rollback technologies to protect system and data. It has free edition for Windows 10/8/7/Vista/XP home computer users.

Step 3: System optimization

  1. Create separate partition for programs and files, do not throw everything into C drive.
  2. Change program default installation path to other partition.
  3. To the programs you've installed to C drive, change the default output path to other partitions. The programs for Games, Videos and Projects output large files.
  4. If the entire hard disk is running out of free space, you'd better replace it with a large one. (NIUBI can help you clone and migrate OS to new disks.)
  5. Run Windows Disk Cleanup monthly to delete new generated junk files.

In Summary

When system C: drive runs out of space on Windows 10/8/7/Vista/XP or Windows Server 2019/2016/2012/2008/2003, clean up disk to get some free space, then add more free space to C drive from other partitions, finally, optimize your system settings. Finish the 3 steps above and you'll fix C drive out of space issue completely.