My daughter's laptop hard drive is failing so I bought a new on. Do I need to buy a new windows operating system now? When we bought the laptop a few years ago there were Windows 10 on it. But now with the new hard drive do I really need to buy a new windows license?
If the original Windows has either an OEM or Retail license then no, you don't need to buy another license.
Since Windows 8.x and the new UEFI that replaced BIOS more than a decade ago, the Windows license is stored in the motherboard itself, not in the systrem drive.
All you have to do is reinstall Windows and it'll automatically activate using the original license.