Windows 11 cannot safely “merge” any two drives with a universal command. Combining space depends on whether you mean adjacent partitions on one disk, Storage Spaces, or physically separate disks.
- Open Disk Management and identify the exact physical disks, partitions, file systems, and where your data is stored.
- Back up all important data before changing partitions.
- If two partitions are on the same disk and unallocated space is directly adjacent in the required position, Windows may allow Extend Volume.
- If separate physical drives need one logical storage pool, investigate Storage Spaces and choose a resiliency layout appropriate to the data.
- Do not delete a partition merely to create unallocated space until its data is verified elsewhere.
Deleting a volume erases its file-system access
Many “merge C and D” tutorials achieve the result by deleting D and extending C. That destroys D’s volume, so a complete backup is mandatory.
Separate disks are not ordinary partition extension
Disk Management generally cannot extend a basic system partition onto another physical drive in the simple way users expect. Dynamic-disk/spanned configurations add failure risk and are not a substitute for a backup.
Recovery and EFI partitions
Do not delete small system, recovery, or EFI partitions because they appear between volumes. They can be required for boot or recovery.
Encryption
Suspend or prepare BitLocker/device encryption according to Microsoft’s guidance before partition changes, and keep recovery keys available.
Kermit Matthews is a freelance writer based in Philadelphia, Pennsylvania with more than a decade of experience writing technology guides. He has a Bachelor’s and Master’s degree in Computer Science and has spent much of his professional career in IT management.
He specializes in writing content about iPhones, Android devices, Microsoft Office, and many other popular applications and devices.