Savvy beta testers have noticed that the option to create an extended partition is no longer available in Disk Management in Windows Vista. Instead, the only option is New Simple Volume. The type of volume this command creates depends on the number of partitions already on the disk. Creating the first, second, and third partition creates a primary partition. Creating a fourth partition automatically creates a logical drive (of the specified size) within an extended partition that is the same size as the remaining unallocated space on the disk. If there is free space left in the extended partition, subsequent partitions on the disk are also created as logical drives.
We made this change to simplify the creation of partitions for novice users, eliminating the need for them to understand the terminology and limits regarding partitions. When users want to create a new partition, Windows Vista will do the right thing on their behalf. Expert users who prefer to create an extended partition themselves, regardless of the number of existing partitions on the disk, can use the DiskPart command-line tool’s CREATE PARTITION EXTENDED command. See KB article 300415 for more information about using this command.