Either by booting from the recovery partition or by booting from the recovery disks that came with the laptop or by booting from the recovery disks you made yourself.
Alas, none of this is standard. So you'll have to find the user manual to see how to it on your laptop.
I have an old laptop running Vista which I would like to give to a friend. Is there an easy way to wipe off all my personal files and folders and programs and leave the computer in the condition I bought it in, without having to reinstall the operating system?