Search by Google and you'll find that many people have the same issue: Extend Volume is disabled for C drive after shrinking D. However, both functions have limitations when repartition hard drive. So Microsoft added Shrink Volume and Extend Volume functions in Disk Management to help resize partition without losing data. Nobody likes to recreate disk partitions, reinstall Windows and all programs. C drive full and low disk space is most common issue on Windows 7 computer, no matter you use laptop or desktop, use SSD or traditional mechanical hard disk for operating system.