Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Yes there is a "Custom" option for Windows 8. When you get to that page, choose "Custom" option. When you get to the page that asks where you want to install, choose your drive and then you'll get the message about there being a windows install there and there will be the windows.old folder. Just be careful on the drive option page that you don't format the drive. That's what erases your files.
Let me know what happens.