With NIUBI Partition Editor, you can increase partition space with unused space in other one without deleting. Comparing with Windows 10 Disk Management, it has advantages such as:
Download NIUBI Partition Editor and you'll see initial disk partition size and structure on the right.
How to increase disk space of C from D:
Step 1: Right click drive D and select "Resize/Move Volume", drag left border rightwards in the pop-up window.
Step 2: Right click drive C and select "Resize/Move Volume" again, drag right border rightwards in the pop-up window.
Full solution to extend partition C in Windows 10.
If you want to increase a 256GB disk to 512GB, it is impossible, because a hard disk is physical unit and disk space can only be transferred inside it. Instead, you can copy to larger disk and replace it. While cloning disk, all partitions inside of it can be extended with extra disk space.
Watch the video how to copy entire disk in Windows 10:
To increase disk space on Windows 10, native Disk Management can only achieve by deleting the adjacent partition. With NIUBI Partition Editor, you can increase partition size by shrinking another one no matter they are adjacent or not. You can also extend partition by copying to larger disk.