one of my friend installed windows 7 on my laptop, so i lost my genuine o.s in my notebook.

[Rams4]

Hi friends, One of my friend used my Notebook and he installed Windows 7, from that day onwards i could not recover my genuine Windows 10 in my notebook, I searched for so many answers but i could not found any answer helpful to my query. I hope my search ends here as it is official page of HP.

[CherylG]

@Rams4

Best way is to order Recovery Media from HP to boot from and reinstall Windows 10:

http://www8.hp.com/us/en/contact-hp/ww-phone-assist.html

You may be able to order it from your Support page in the list of software/drivers:

https://support.hp.com/us-en/drivers

OR_Your Windows 10 license key is embedded in BIOS and you can reinstall Windows without HP Recovery Media. Microsoft provides the free Media Creation Tool to download files and create a Windows 10 usb flash drive.Advantage is you will have latest updated version of Windows 10. At least 8gb flash drive required:

https://www.microsoft.com/en-us/software-download/windows10

Select Download tool now,save it,then Run.
If you agree to the license terms, select Accept.
On the What do you want to do? page, select Create installation media for another PC, and then select Next.
Select the language, edition, and architecture (64-bit or 32-bit) for Windows 10.
The Guide here shows the steps.Pay attention to Step 5 if you will be using another pc. If you use the laptop to make it just skip that step:
https://www.tenforums.com/tutorials/2376-create-bootable-usb-flash-drive-install-windows-10-a.html