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.
Upgrading is the most convenient way to get Windows 7 on your computer, because it keeps your files, settings, and programs from Windows Vista in place.
If your current edition of Windows Vista can't be upgraded to the edition of Windows 7 that you want to use, you can still install Windows 7 by using the Custom installation option instead. However, the Custom option doesn't preserve your files, programs, or settings. For a step-by-step tutorial on how to perform a custom installation, see Upgrading from Windows Vista to Windows 7 (custom installation).
Make sure that your programs and devices will work with Windows 7
Since your computer is running Windows Vista, it meets the system requirements for Windows 7. We still recommend that you download and run the free Windows 7 Upgrade Advisor from the Windows 7 Upgrade Advisor webpage on the Windows website. It helps find potential issues with your computer’s hardware, devices, or programs that might affect installing Windows 7, and gives recommendations on what to do.
Also, go to the Windows 7 Compatibility Center to see what works with Windows 7 and find direct links to drivers, updates, and downloads.