What does Vista say about it? Look in the Disk Management utility
in Vista. It will clearly identify the primary and logical partitions. And in the graphic depiction of the drives and partitions, the primary partitions are color coded with a dark blue stripe, the logical partitions have a bright blue color stripe, and the extended partition enclosing the logical partitions is green.
Here is an example
of XP's Disk Management utility which looks just like Vista's. Disk 1 has three primary partitions and one extended partition. But the extended partition has a bunch of logical partitions.
P.S.: The partition table of every hard drive actually exists in the master boot record of the drive (the very first 512-byte sector). The partition table part of the master boot record is only a mere 64-bytes long and contains basic information such as type, size, start, end, active flag, etc. Those 64 bytes have room for the information about four primary partitions or three primary partitions and one extended partition. The concept of an extended partition was invented by Microsoft and IBM years ago when it became evident that four partitions were not going to be enough. There is theoretically no limit on the number of logical partitions that can exist inside an extended partition. But there are practical limits. Windows systems use letters for partitions, and the total number of partitions is limited by the number of letters in the alphabet (sort of). Recent Fedora systems (since F7) are limited to a total of fifteen partitions by the libata driver code that is used for all drives since then. The partition table for the logical partitions is daisy-chained across the boot sectors of every logical partition. The boot sector of each logical partition contains partition table information about itself and the next logical partition. The very last logical partition has information about only itself, of course.