How to Extend a Partition to Fill a Computer Drive
Choose Disk Management from the Computer Management window’s left pane.
The window’s right side displays your disk drives and their partitions. Your C partition is identified by the characters (C:), along with the words System, Boot File, Page File, and other technical verbosity. (It also has a blue line across its top.) The space to the right on your C drive is listed as Unallocated, meaning it’s not being used. (It has a black line across its top.) So, your mission is to extend your C partition’s boundaries to grab that unused space.