Laptops usually come preinstalled and pre-activated with a genuine key. Your windows key is usually on a sticker on the bottom of your laptop.
If your laptop is currently working then you can also install a piece of software called
SIW which can be used to look up your key from within your computer (Install and run it, then go to
Software >
Licenses) and then you can simply write it down. Keep your key in a secure place and never share it over the internet.
SIW and many other fine products can be found in our
Freeware DB.