This document provides step-by-step instructions to install Windows 7 on a machine with at least 20GB of unallocated space. The steps include booting from the Windows 7 DVD, selecting installation options like language and keyboard, accepting the license agreement, partitioning the unallocated space, completing the installation process which may require several restarts, setting up a username and password, activating Windows 7 with a product key, configuring time zone and location settings. Upon completing all the steps, Windows 7 installation is finished.