Final answer:
Windows Vista Business and Windows XP Professional 64-bit can be upgraded directly to Windows 7 Professional by a default installation.
Step-by-step explanation:
The operating systems that can be upgraded directly to Windows 7 Professional by a default installation are Windows Vista Business and Windows XP Professional 64-bit.
Windows 7 Home Premium, Windows XP Home, and Windows XP Media Center cannot be upgraded directly to Windows 7 Professional by a default installation.
It is important to note that to upgrade from Windows XP Professional 64-bit to Windows 7 Professional, a clean installation is required, meaning the user will need to perform a fresh install of the new operating system.