Hello, I have Windows 8.1 Installed on this laptop and a USB thumb drive that has Windows7 image installed. I wanted to boot up my system to usb so I can install Windows7 to this machine, but I couldn't. Normally, other computers I have would let me choose how I would like to boot, but this one will just go straight to Windows 8. I have tried del, f1~12 buttons when lenovo screen comes up during start up. But it wouldn't let me. =(