depends on the OS... Sometimes it is F4, F11, shift+F11...
from Lenovo support... NOT specific to your laptop:
Using the Product Recovery program on the hard disk
Note: All personal data in the computer will be lost during the recovery procedure.
Follow these steps:
Pressing F11 will start the Product Recovery program. When you see the Product Recovery Program Main Menu, select Full Recovery or Factory Contents and follow the instructions on the screen.
After the software has been reinstalled, copy your personal configuration and data files back into their original directories on the hard drive. Obtain more detailed instructions.