(Enterprise Windows 7 Home Premium
Sold as basic version in USA, UK, etc.

* Full Windows Aero
* Home Group (create and join)
* Multi-Touch
* Premium Games
* Media Center

Windows 7 Professional
For business use.

All features of Windows 7 Home Premium +
* Windows Server Domain
* Remote Desktop Server
* Location aware printing
* Encryption
* Presentation

Windows 7 Ultimate (sold as Enterprise to large companies)
For enthusiasts and high-end PC's.

All features of Windows 7 Professional +
* AppLocker
* BitLocker Drive Encryption
* BranchCache Distributed Cache
* DirectAccess
* Multilingual User Interface Pack
* Virtual Hard Disk Booting