Until now, Windows Vista was the most secure version of the Windows operating system. Windows 7 picks up where Vista left off, and improves on that foundation to provide an even more secure computing experience
Windows Vista BootScreen pointless, but Microsoft decided to cover an extra visually attractive boot screen that can be simply switched with very small trouble.
Depending on your hardware and your current edition of Windows Vista, you can use the Upgrade option during Windows 7 installation to upgrade from Windows Vista to a corresponding or higher edition of Windows 7.