Microsoft has released an update for Windows 7 official diagram explaining the upgrade paths for Windows XP and Windows Vista to Windows 7 The diagram shows that, indeed, that must have a clean install of the operating system or upgrade an operating system directly. Ed Bott pointed out that the letter is too confusing for the average user, and had at least one product that does not exist. Most of the information displayed in the graph is redundant.
Microsoft will probably try a deep 32-bit and 64-bit editions on separate lines. It would be much easier to read, through the combination of these two lines in an upgrade path is the same for both 32-bit and 64-bit editions. That removing not existing 64-bit Vista Starter Edition, the diagram in a readable format is easy to understand.