Some people—for whatever reason—are still using Windows 7. If you own a computer running Windows 7 and would like to start afresh with a clean operating system, you’ll need a copy of the necessary installation files. Keep reading to find out how you can legally download and install Windows 7 OEM. What Is Windows 7 OEM? If Windows 7 came pre-installed on your machine when you bought it, you probably didn’t get a copy of the Windows 7 installation DVD.