Better than the old Windows XP and Server 2003, Windows 7 and subsequent versions has new Shrink and Extend Volume functions in Disk Management to help resize partition without losing data. Comparing with data volumes, system partition C is very likely running out of space. It can't be better if you can increase C drive space without wasting a long time to start over. But if you want to extend C drive with Disk Management, you'll be unsatisfied, because Extend Volume function is always greyed out. This article introduces why the option to extend system C drive greyed out and how to fix this issue.
Firstly, you should know that the size of a physical hard disk is fixed, before extending a partition, there must be free Unallocated space. To get such space, you may either delete or shrink another volume on the same disk. If you right click C drive in Disk Management without available Unallocated space, of course Extend Volume is grayed out.
The most common issue is that Extend Volume still greyed out for C drive after shrinking D or other partitions. As you see in the screenshot, I got 20GB Unallocated space after shrinking D drive, but the option to extend C drive still greyed out.
This is because Extend Volume function can only merge Unallocated space to the left contiguous partition, but Shrink Volume can only make Unallocated space on the right.
Unallocated space shrunk from D drive is non adjacent to C drive, so Disk Management cannot extend C drive with this Unallocated space.
The only way to extend C drive in Disk Management is by deleting the right contiguous partition D. If there is no or you cannot delete this partition, Disk Management is useless. After deleting D drive, you'll get available space next to C drive. Then in GPT disk you can extend C drive with Extend Volume function, but in MBR disk, it depends.
As you see in the screenshot, Extend Volume still greyed out for C drive after deleting D and E.
This is because: Free space deleted from Logical drive can't be extended to any Primary partition, Unallocated space deleted from Primary partition can't be extended to any Logical drives. If drive D is a Primary partition in my computer, there is no such issue. If Disk 0 is a GPT disk, I can also extend C drive by deleting D.
Extend Volume functionality is added from Windows Vista, so in Windows XP and Server 2003, when you right click C drive there's no Extend Volume option.
With NIUBI Partition Editor, these problem can be solved easily.
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