John partitioned his hard drive and he's noticed that his C drive has less room than his D drive. Leo says that is likely because Windows and other apps are filling up that C drive. John could move the data to his D drive and that would free up space. He could repartition or undo the partition. Depending on how the D drive is laid out, he can hit Windows + X and open the disk management tool. Click on the C partition and expand it. If that doesn't work, EaseUS has a disk partitioner. But the safest way is just to get an external hard drive, move data onto it, and then reformat the computer hard drive, reinstalling Windows and the apps to a full-size C drive.