Hi,
Thanks for posting on our forum!
Basically, there are three scenarios where you cannot extend your volume:
1.The partition users want to extend is not a NTFS partition. Microsoft says extending volume feature in Disk Management only works to a raw or NTFS partition.
2.There is no unallocated or free space on hard disk or the space is not contiguous and after the partition which needs extending.
3.Users want to extend a primary partition/logical partition, but there is just a free space/unallocated space right after the target partition.
Obviously, your condition is 2) and as @Anonymous suggested, we recommend you to either backup your New Volume E and delete that partition then try to extend C: volume again, or you can use some third-party tools like EaseUS Partition Master. Here is an example on how to fix Can't Extend Volume Error with No Adjacent Unallocated Space:
https://www.easeus.com/partition-master/cannot-extend-volume.html
Please note: Information posted in the given link is hosted by a third party. Microsoft does not guarantee the accuracy and effectiveness of information.
Thanks for your support! Besides, would you please help me Accept Answer. An accepted blog can be put on top of our forum, so that people who have a similar issue can get access to their solution more quickly. I would really appreciate it if you could support my work.
BR,
Joan
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