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#1
Hello sonugsaroj, and welcome to Seven Forums.
Did you solve this since you have this thread marked solved?
If not, then you should be able to right click on the green partition, and click on "Delete" until it shows as "Unallocated".
Afterwards, you could extend C: into the "Unallocated" space to add it back to C.
Hope this helps, :)
Shawn