POTENTIAL POINTS OF CONFUSION
In addition to the wealth of information, above, there are some issues worth discussing in detail.
• Lots of editions. There are a confusing number of Windows 7 editions. However, most home users can concentrate on just three: Home Premium, Professional, and Ultimate.
• Upgrade editions. Each of these three editions has an "Upgrade" version which is already available for pre-sale. For these upgrade versions, all of the same upgrade paths are available with one caveat: there must be an activated version of Windows currently installed on the system to be upgraded. You cannot use these to clean install a brand new system with no OS.
• 32-bit and 64-bit. Windows 7 retail boxes will not be specific to 32- or 64-bit architectures. Each edition will allow you to install the 32-bit OR the 64-bit version. If you have multiple license keys, you can install one 32-bit or 64-bit Windows for each key.
• In-place Upgrades. There are a small set of circumstances in which you can perform an "in-place upgrade". This allows you to install Windows 7 on top of Vista without needing to format your hard drive partition. An in-place upgrade will keep all of your installed applications (provided they are compatible) and your settings, documents, and other data files. This can only be done for the same architecture (32- or 64-bit) and the same or higher edition. So Vista Home Premium can be upgraded in-place to Windows 7 Home Premium (same) or Windows 7 Ultimate (higher). However, Vista Ultimate cannot be upgraded in-place to Windows 7 Home Premium or Professional because these are lower editions.
• Anytime Upgrades. The Anytime Upgrade is an electronic purchase of a higher edition of the *current* Windows. This can only be used to upgrade Vista to a higher Vista or Windows 7 to a higher Windows 7. So, if you purchased Windows 7 Home Premium then later decide that you want the features in Ultimate, you can use the Anytime Upgrade to unlock the extra features without needing to do a new install. Note that Ed Bott's chart (above) shows an Anytime Upgrade option from Vista to Windows 7. This is a two step process involving an in-place upgrade (Vista to 7) followed by an Anytime Upgrade (7 to 7).