Failing Win 10 Hard Drive .. how to reinstall Win 10 on a new HD

Hi, the Tutorial section can be a good friend.
Clean Install Windows 10 | Windows 10 Tutorials

You can freely download Win 10 iso's, and create a bootable medium to install it.
Activation should be automatic as you've already had it installed.

Note that if your Win 10 was an older build, by default you will be installing build 1803. A change in major Windows build may be significant for you.

Windows 10 Tutorial Index | Windows 10 Tutorials
This is worth bookmarking- then you can search the pages.

Windows 10 Tutorial Index | Windows 10 Tutorials
Create Bootable USB Flash Drive to Install Windows 10 | Windows 10 Tutorials

How do you avoid clean installing in many circumstances- even if your drive fails?
Use disk imaging routinely as we so often urge users to do. E.g. Macrium reflect (free) + large external disk for disk image sets.

How do you detect early disk failure?
Use a monitoring and reporting program that generates alerts.
E.g. Crystal Diskinfo (free).

You may wish to take the opportunity to upgrade to a SSD. If so, make sure AHCI protocol is enabled for best performance. (10-13s boot to lock screen e.g.)

You're welcome and credit to Brink for the great tutorials.

Once you have your PC running again, you can really help yourself by starting to use disk imaging routinely as early as you can, creating the first before installing more and configuring.