Windows 7 Extend Volume grayed out.

[davidhk129]

Win 7 Home Premium.

I was doing dual boot with Win 7 and Win 10 TP.
I decided to remove the dual boot.
So, I went to disk management and removed the volume where Win 10 was. The trouble is, the partition should be marked as unallocated. Instead it is marked as free space.
Now, I right clicked at C and the Extend Volume is inactive.
How do I fixed that?

P.S. I did the same thing on my other laptop dual booting Win 8.1.1 Pro and Win 10 TP, and I was successful removing the dual boot and extend the volume back to C.
But this time, something I did went wrong.

 

[davidhk129]

Never mind.
I've fixed that.

Thank you.

 

[Anna Lan]

Because you already have three primary partitions, so when you take any space out, it would go into extended partition. If the space belongs to extended partition, it would be marked as FREE SPACE, if it belongs to primary partition, it would be marked as UNALLOCATED.