05-10-2016 06:48 AM - edited 05-10-2016 06:56 AM
You have to re-install Windows (64-bit version) again, using a USB or a ODD and boot it trough the BOOT-menu on startup.
When Windows is installed you have to optimize your computer by installing drivers.
I've included a link to the Y50-70 drivers below. Be sure to pick the right operating-system!
To clarify: You have to purchase Windows in order to install it. You can either do it by ordering a recovery media from Lenovo (please Google) or trough another reseller.
05-10-2016 11:42 AM