Windows 7 Ultimate: this is the most versatile and powerful edition of Windows 7. It combines remarkable ease-of-use with the entertainment features of Home Premium and the business capabilities of Professional, including the ability to run many Windows XP productivity programs in Windows XP Mode. For added security, you can encrypt your data with BitLocker and BitLocker To Go. And for extra flexibility, you can work in any of 35 languages. Get it all with Windows 7 Ultimate.
Windows 7 Home Premium - Windows 7 Home Premium makes it easy to create a home network and share all of your favourite photos, videos and music. You can even watch, pause, rewind and record TV. Get the best entertainment experience with Windows 7 Home Premium. Get Windows 7 Home Premium.
Windows 7 Professional - With Windows 7 Professional, fewer walls stand between you and your success. You can run many Windows XP productivity programs in Windows XP Mode and recover data easily with automatic backups to your home or business network. You can also connect to company networks effortlessly and more securely with Domain Join. With all the exciting entertainment features of Windows Home Premium, it's a great choice for home and for business. Need to use multiple languages on your PC or help protect your data with enhanced BitLocker security? Get Windows 7 Professional.
Windows 7 Starter - This is a very limited edition if Windows 7, designed more for the emerging Netbook market than anything else (Which Microsoft failed to plan for when they released Windows Vista), Starter Edition will have a 3 app limit (Excluding System Processes), on opening the 4th you will be prompted to upgrade. Other stuff you will miss out on are as follows: No personalization options (changing background images/wallpapers or sounds), No Aero, No DVD playback, No Media Center features at all, No domain support, No XP virtualization mode, No multi-monitor support. Find out more on Windows 7 Starter here.
Windows 7 Enterprise - The Windows 7 Enterprise operating system is available to Microsoft Software Assurance customers (Business Bulk Buyers) only. Enterprise edition is Windows 7 Professional plus "DirectAccess", "BranchCache", "Enterprise Search", "Bitlocker", "Bitlocker to go", "Applocker", "Virtual desktop infrastructure (VDI)" and "Multilingual Interface". Find out about more on Windows 7 Enterprise here.