Recently I was reading a lot about the structure of harddisk and how OS uses the partitions. Primary partitions are the only one that are bootable. They’re always the C: drive when active. Normally you can only have one Extended partitions are needed when you want more than one partition. You can only have ONE Extended partition. Logical Drives come into the Extended partition. They are handy since you know that you can only have one Primary and one Extended so you can get more than only two partitions. They would be your D:, E:, etc. drives.