>>15499131. Get a USB with at least 8gb
2. Download the version of windows you want (afaik microsoft will only let you download 11, but you can just look up 'windows 10 iso internet archive' or 8 or 7 or whatever one you want)
3. download rufus (
https://rufus.ie/en/#download (standard version x64))
4. plug your usb in a computer, boot up rufus, select the windows .iso file you downloaded
5. look up a rufus tutorial or whatever if you need to, but it's easy to figure out
6. when done, plug the usb in your laptop turned off and then turn it on
7. repeatedly press the Delete key real fast while your laptop turns on to get in the BIOS (if Delete doesn't work try F2)
8. in the BIOS look for the boot order, there should be a list with items like "HDD 9437522gb" "USB 7.9gb" or something like that
9. Find your USB in it, it should say something like USB XXXgb where XXX is roughly the size of the usb so for example a 8gb one would say maybe 7.8gb a 32gb might say 28gb, just look for something close to your USB size
10. move your USB to the top of the list, save and exit
11. your laptop should now boot with the .iso file in your USB, follow the intructions on the screen to install windows (it's normal for your laptop to take hours to install windows don't worry, it's not stuck)
That'll erase all data in your laptop in the process. You said you don't care but if you want to salvage data from it before you reinstall windows you can remove your HDD from the laptop and hook it up on another computer to access the files without needing the password.
Feel free to ask if you need any more clarification.