Hi Arvind
When you purchase a new PC or laptop these days, it does not come with a Windows DVD or Product key, because Windows 10 licencing is very different to previous versions
When you initially activate Windows 10 on that new laptop, a digital signature for that is generated and stored on the Microsoft Activation servers, then should you ever need to re-install Windows 10 on that laptop , once you install the same edition (Home, Pro . . etc) it will self-activate once it is put on the Internet
If you encounter problems with Windows 10, it has its own built-in Recovery Environment that has many options, including resetting Windows 10 factory settings
If you ever need to re-install Windows 10, you can always download and create bootable Windows 10 installation media on an 8GB flash drive and that will be the best method, since it will contain the latest version of Windows 10
Click this link:
https://www.microsoft.com/en-us/software-downlo...
to download the Media Creation Tool (Click on Download Tool Now), with that you can download the latest Windows 10 ISO (Select Create Installation Media for Another PC), you can create a bootable USB flash drive (min 8GB) using that tool