According to the report, users coming from Windows 7 Starter, Home Basic, Home Premium, Windows 7 Professional and Ultimate, will be able to upgrade to Windows 8 while maintaining the existing Windows settings, personal files and applications.
Coming from Windows Vista without SP1 and Windows XP SP3 will be able to upgrade to Windows 8, but in this case will be maintained only personal files, the rest will be lost. With the SP1 of Vista SP1 will be able to keep all personal data and system settings. Finally, those wishing to migrate from 32 to 64 bits will be forced to proceed with a clean installation.