Microsoft has revealed to select partners the details on upgrading to Windows 8 from older Windows releases. There are some limitations as to which of the latest Windows 8 versions older generation Windows releases can upgrade to and whether those upgrades will be able to retain personal data and system settings.
According to ZDNet's industry sources, users upgrading to Windows 8, the entry-level consumer version, from Windows 7 Starter, Windows 7 Home Basic, and Windows 7 Home Premium can maintain their existing Windows settings, personal files and applications. This goes the same for users upgrading to Windows 8 Pro from Windows 7 Starter, Windows 7 Home Basic, Windows 7 Home Premium, Windows 7 Professional, and Windows 7 Ultimate. And, this also applies to users upgrading to Windows 7 Enterprise from Windows 7 Professional and Windows 7 Enterprise.
However, users upgrading to Windows 8 from Windows Vista without SP1 installed will only be able to retain personal files and not any existing Windows settings. If SP1 is installed prior to upgrade then personal data and system settings will be maintained. But, users upgrading to Windows 8 from Windows XP with SP3 or higher will only be able to retain personal files.
Also, users upgrading a cross-language installation will not be able to keep their Windows settings, files, or applications. Users using cross-architecture installations, as in 32-bit to 64-bit, will not be allowed to upgrade this way.