manual
http://www.lenovo.com/shop/americas/content/user_g uides/ideapad_y410py510p_ug_english.pdf#page=30

How can I change the boot mode?
There are two boot modes: UEFI and Legacy. To change the boot mode, start the BIOS setup
utility and set boot mode to UEFI or Legacy support on the boot menu.
When do I need to change the boot mode?
The default boot mode for your
computer is UEFI mode. If you need to install a legacy
Windows operating system (that is, any oper
ating system before Windows 8) on your
computer, you must change the boot mode to
Legacy support. The legacy Windows operating
system cannot be installed if you don’t change the boot mode