In most of Windows computers, if you did not create a large C: drive and optimize it regularly, you'll encounter the problem that system C: drive is running out of space sooner or later. What to do when it happens? Nobody likes to start from scratch. There's plenty of free space in another D drive, so many people wonder if it is possible to shrink D to expand system C drive without losing data. The answer is yes, however, you'd better back up first and run safe partition software, because there's potential system damage and data loss risk while repartition hard drive with unreliable software.
In Windows XP and Server 2003 Disk Management console, you can only do basic operations such as create, delete and format partition, so you cannot shrink D and extend C drive with it. In Windows 10/8/7/Vista and Server 2019/2016/2012/2008, there are advanced Shrink Volume and Extend Volume functions built in Disk Management. But, it can only help you shrink NTFS partition to create new volume(s), it cannot extend C drive by shrinking D or any other volumes.
As you see, Extend Volume greyed out for C drive after shrinking D, why? From Microsoft explanation, to enlarge a drive with Extend Volume function, there should be adjacent Unallocated space on the right side.
Unallocated space shrank from D drive is nonadjacent to C, of course Extend Volume doesn't work.
Windows has another Diskpart command tool that is able to shrink and extend partition, too. Unfortunately, the same with GUI Disk Management, it cannot shrink D to expand C drive. So you need 3rd-party program to complete this task. For Windows 10/8/7/Vista/XP users, there is free partition software such as NIUBI Partition Editor Free, which is 100% clean without any bundles.
Download and install NIUBI Partition Editor Free edition, you'll see the main window with disk partition information and available operations.
You just need to drag and drop on the disk map, follow the steps to shrink D and extend C drive on Windows PC & Server:
This software is designed to work in its virtual mode, the operations you do will be listed as pending on bottom left, and real disk partitions won't be modified until click Apply to confirm.
In some computers, drive D is on another hard disk. In that case, no software can shrink D to expand system C drive, because a 256GB physical disk can't be decreased to 200GB or increased to 300GB.
To expand C drive under this situation, you need to copy system disk to another larger one. Follow the steps in the video:
If you want to extend C drive for a virtual machine in VMware or Hyper-V, simply follow the steps above to shrink D and expand C drive when there's plenty of free space in D drive. If there's no available free space in D and other volume on the same disk, you can increase virtual disk size in VMware and Hyper-V. After that, additional disk space can be added into C drive without copying to other disk.
Besides shrinking, moving, extending and copying disk partition, NIUBI Partition Editor helps do many other operations such as convert, defrag, hide, wipe partition and scan bad sectors. Better than other software, it has advanced technologies to protect system and data such as: