How to remove Windows 8 and install Windows 7 on a Lenovo ideapad z580 laptop

My friend just bought a new Lenovo ideapad z580 laptop with Windows 8 on it. She was not sure if her special statistical programs will run on Windows 8, so she asked me to remove Windows 8 and install her copy of Windows 7  64 bit on it. As it turned out the Lenovo laptop […]