How many different versions of Windows Vista are there?

Microsoft is planning to release the following Windows Vista editions:

Windows Vista Starter Edition
This edition is for emerging markets and designed for entry-level PC users.

Windows Vista Home Basic Edition
For homes with basic computing needs

Windows Vista Home Premium Edition
Windows Vista Home Premium includes everything in Windows Vista Home Basic, along with additional features such as the user interface Windows Aero, integrated search, Windows Media Center, Windows Tablet PC technology, and integrated DVD.

Windows Vista Ultimate Edition
This edition comes with all features including entertainment features, mobility features and business-oriented features

Windows Vista Business Edition
This edition is for organizations of all sizes and includes the new Windows Aero user interface and TabletPC technology

Windows Vista Enterprise Edition
This edition includes everything in Windows Vista Business Edition and the following additional three features: Windows BitLocker Drive Encryption, Virtual PC Express, and Subsystem for UNIX-based Applications.