It is not necessary to reinstall the system to separate a single C drive into C and D in Windows. Microsoft’s description of Disk Management is based on the built-in tool; As with previous Windows 11 performance settings, it is necessary to back up important files before starting.
After right-clicking on the Start button and opening Disk Management, drive C is selected. The “Shrink Volume” command asks how much of the free space to allocate. Since the entered value is in megabytes, the planned D drive capacity must be calculated accordingly.
When the reduction is completed, an “Unallocated” space is created, shown with a black stripe. When you right-click on this area and select “New Simple Volume”, the wizard shows drive letter, size and file system options.
The letter D can be assigned if it is blank and NTFS will be selected for most users. When the quick format is complete, the new drive appears in File Explorer. The process does not move files on drive C; It just allocates the free space to the new partition.
System partitions should not be touched
Small partitions marked EFI, recovery, and OEM can be used to boot or recover Windows. Deleting or formatting them may cause the computer to not start. Only the main data section should be processed.
If the “shrinkable space” is less than expected, system files that cannot be moved may have created a limit. Therefore, before switching to third-party tools, backup, free space and disk health should be checked. If BitLocker is turned on, make sure the recovery key is accessible.