1. No matter how many partitions a drive is divided, by default a drive can be divided only twice and that never changes - a Primary DOS Drive and an Extended DOS Partition (click to see an example screenshot). Even though a hard drive must contain a single Primary DOS Partition to be formatted and if it is not divided further, it should be referred to as a drive in my opinion and not a partitioned drive
2. A Primary DOS Drive is assigned the drive letter C -- in theory, the drive set Active which boots a system. If a computer has more than one physical hard drive, each separate drive has its own primary partition and becomes the next drive letter. As an example with three physical drives, the first is assigned drive letter C, the second drive letter D, and the third drive letter E.
a. If all hard drive space is included in a single partition, no Extended DOS Partition may be created.
b. If all hard drive space is not included in a single partition, 100% of the remaining space may be used to created an Extended DOS Partition where that space can then be divided into usable logical volumes into whatever percent wanted -- one or more which then becomes drive/partition letter F, etc.
3. However, it is possible to partition a separate drive by creating an Extended DOS Partitions that causes the drive letter(s) to be added after those already existing. Can you imagine what would happen should the existing drive letter(s) change, [Q51978]?