Why Cannot Extend C Drive Windows 10

My C drive is out of space, and I tried to extend the C drive via Disk Management. The problem is that the Extend Volume option is unavailable. Why can't I extend the C drive on my Windows 10? What else can I do to manage that? Thanks in advance!

Here are a few reasons why you cannot extend the C drive on a Windows 10 PC:

  • No unallocated space on the disk.
  • You can't extend the primary partition with unallocated space from an extended partition.
  • No adjacent unallocated space behind C drive.
  • File system limitation.

If you want to extend the C drive without Windows restrictions, I suggest you download a third-party disk partition manager like EaseUS Partition Master Professional.

Regardless of the actual reason why you cannot extend the volume, this tool can help.

For no unallocated space issue, you can:

Step 1. Launch EaseUS Partition Master and select a partition with a large additional space.

Step 2. Choose "Allocate Space," select C drive as the destination partition, and adjust how much size you want to add to the C drive.

Step 3. Then, click "OK" and execute the task.

You can also use the "Extend with 2nd Disk" feature to extend the C drive with the space from another disk.

Related article: [100% Fixed] Can I Extend C Drive from Another Disk in Windows 10/11?

For case 2, 3 and 4:

Step 1. Open EaseUS Partition Master, and select the C drive.

Step 2. Choose "Resize/Move" and drag the dot to modify the storage space of the C drive.

Step 3. Then, click "OK" and execute the task.