Are you planning on getting a new larger drive or are there multiple partitions on the drive that contains volume C?
If you are getting a new larger drive, you can clone your current drive onto the larger drive. If your current drive has multiple volumes, you can use disk management to expand the volume as long as there is no adjacent partition. You could also use a 3rd party partition manager to try to expand the partition in place. If you plan on messing with the partitions, be sure to make a backup of the drive first just in case something goes wrong.
Almost forgot the answer... none of these will require a format.