How do I reinstall a preinstalled version of Windows?

Some computers that come preinstalled with Windows often have what is called a recovery partition. This is used to reinstall the operating system in the event of a system crash. To access it, you will need to boot into when you start your computer by pressing a function key.

Can I reinstall Windows 10 in a laptop that came pre installed with Windows 10 after formatting it?

Anytime you need to reinstall Windows 10 on that machine, just proceed to reinstall Windows 10. It will automatically reactivate.