If your current version of Windows can be upgraded to Windows 7, choose Upgrade to keep your files, settings, and programs from your previous version of Windows. This is the simplest installation option. To learn more about which versions of Windows can be upgraded to Windows 7, go to
Upgrading to Windows 7: frequently asked questions on the Windows website.
If your version of Windows can't be upgraded, you need to choose Custom. However, the Custom option doesn't preserve your files, settings, and programs. It's sometimes referred to as a clean installation for that reason. You'll need to back up your files and then restore them after installation is complete. You'll also need to reinstall your programs, so make sure you have the installation discs and product keys for the programs you want to use in Windows 7, as well as the setup files for any programs you downloaded from the Internet.
You can also use the Custom option to perform advanced disk management tasks during installation, such as creating and formatting partitions on your computer's hard disk, or choosing a specific partition on which to install Windows 7. For more information, see Installing and reinstalling Windows 7.