My computer is completely frozen up, keeps saying repairing disc for eight hours now!.
Are you planning on acquiring a new hard drive to use for the install?
I would like to re-install Windows 10. I cannot find the product key code anywhere on my HP LAPTOP computer
IF your computer was previously running Windows 10, then.....
You do not need a product key in order to perform a clean install or re-install of Windows 10. Your computer is logged with Microsoft as having a digital license and as such you can re-install Windows 10 whenever you wish, as long as you don't exceed the allowable hardware changes.
how do I remove my previous version of Windows?
Typically you can just boot from the installation media and choose to "Custom" install when offered the opportunity.
Then you can choose to delete any partitions that apply to your previous installation(s) and then choose the new unallocated space to host the new custom installation.
WARNING:
IF the physical hard disk is failing or has failed then it may not support any type of installation
THE hard disk may contain one or more factory partitions that are normally used for a factory reset. You may want to leave them in place and not remove them. You might even want to contact the system manufacturer to see how you might use them to restore the computer to factory fresh installation, OR
See if they have factory installation media available that you might be able to use to recover the computer.