C drive is running out of disk space in Windows Server 2016.

I am running Windows Server 2016 on my server at work and the C drive is running out of space and has less than 100 megabytes left. This server is made the C drive 30 gigabytes and another D drive, 300 gigabytes. I am wondering if it is possible shrinking the D drive and expanding the C drive to make more room.

This is typical question on Windows Server 2016. Most of the server administrators encountered such problem that system C drive is running out of space or becomes almost full. Meanwhile, there is plenty of free space in D or other drives. In this situation, two steps:

  1. Reclaim free space with Windows built-in Disk Cleanup, so you can get more precious free space. Otherwise, if C drive is almost full, it may cause system stuck or crash. Disk Cleanup is very useful to the server that never free up disk space.
  2. Add more free space into C drive from other volumes. If you cannot free up plenty of free space, you’d better increase C drive free space, otherwise, you’ll see C drive full in near future.

In this article, I’ll give both detailed steps to fix C drive running out space on Server 2016.

First step – free up disk space

About freeing up space, I always suggest Windows built-in Disk Cleanup, because I have used it in most of the Windows editions MANY times. To me, it is a good tool. Here I won’t introduce other ways such as using 3rd party software or deleting files manually.

Steps to free up disk space with Disk Cleanup:

Step 1: Open Windows Explorer, right click C drive and select “Properties“.

Step 2: Click “Disk Cleanup“, (you may also click the option to compress this drive to save more disk space).

Disk Cleanup

Step 3: In next window, click the check-box in front of the files you want to clean.

Select files

Step 4: Click OK and confirm this operation.


My test server is new installed, so there is little space can be reclaimed.

It is easy and fast to complete this task. However, some servers cannot reclaim much free space, the main reason C drive running out of space is not filling up by junk files, but too small disk partition. To save disk space, some people create the C drive 30GB – 50GB, it is too small. C drive of some factory server is not big enough. In this situation, you should complete the Second step to resize disk partition and increase C drive size.

Second step – increase C drive space

Different with other read-only applications, partition software will move files and modify the disk partition parameters, so it is important to select a reliable software, because a bad designed software may cause system failure, partition corruption or data loss.

Here I recommend NIUBI Partition Editor, which integrated Enhanced Data Protection technology to keep operating system and data intact, even if power failure or other hardware issue occurred. Furthermore, it is 30% – 300% faster than other tool to resize partitions. Save much time especially when there are large amount of files in the partition that you want to resize. Data safety and time are most important to a server.

Steps to add more free space into C: drive:

Step 1. Download and install NIUBI Partition Editor, right click volume D and select “Resize/Move Volume“.

Resize volume

Select Resize

Step 2: In the pop-up window, drag left border rightwards to take free space out from D.

Drag to shrink

Shrink d drive

Drag to shrink

Click OK and back to the main window, 20GB Unallocated space created behind C: drive.

Unallocated created

Step 3: Right click C drive and select “Resize/Move Volume” again. In the pop-up window, drag the right border rightwards to hold the Unallocated space.

Drag to extend

Extend C drive

Extend C

Step 4: Click OK and back to the main window, C drive increased to 60GB by adding the Unallocated space. Click Apply on top left to execute, done.

C drive extended

In Summary

When system C: drive is running out of space on Windows Server 2016, try to free up disk space with Disk Cleanup, and then increase C drive free space with server partition software. What to do if there is not plenty of free space in volume D? Simply get free space from other volumes in the same disk.

Video guide to add free space into C drive


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