If you're buying a netbook with Windows 7 installed, you may be sold one of them: Windows 7 Starter - a special 'netbook edition' only sold pre-installed on new computers. That's four of the six editions covered, but there are two odd ones left. Don't worry about buying it for the kids. The most likely time you'll run into it is if your employer says, 'Oi, newbie, use this laptop,' or if you're an IT professional managing virtual machines and network privileges. It incorporates all the features of Windows 7 Home Premium and Professional, but adds support for enterprise-level technologies for use in corporate environments. Windows 7 Enterprise is aimed at the larger businesses of the world, not home users.

It won't be sold on shelves in the UK, and you needn't be confused by its existence. It lacks perks such as Windows Media Centre and multi-touch navigation. Home Basic is a stripped-down edition to be sold in developing markets, such as China, Brazil and Thailand, where Microsoft can charge less in order to tackle rampant piracy. There are a couple of versions you'll likely never even see on shelves: Windows 7 Home Basic and Windows 7 Enterprise. If you're just the average consumer with a new PC, these are the two editions to decide between.

Essentially, it's for any computer that will spend half its life at your home, and the other half at the office.

It contains all the features of Home Premium, but adds support for Domain Joining, which you may need to log on to your office's corporate network Windows XP Mode, which makes old software that's incompatible with Windows 7 run as if it was running on XP and Microsoft's Backup and Restore Centre, which is an integrated file and folder backup utility for automated backup of important files. If the answer to these question is yes, you should buy Windows 7 Professional.

Windows 7 enterprise