If you have upgraded from Windows 7 to Windows 8, and based on the version used you can use "the Uninstall a program" option for downgrading. Basically, the update can be reversed if you have that entry on the list, just like you would uninstall a program. If there is nothing on the uninstall list of programs you will need to perform a new installation of Windows 7. Doing things manually increases chances of bricking your computer.
