OS missing or corrupt

You need another PC to create a bootable USB, ask for a friend if you don't have one:

• Create a bootable USB install media (video here)
• Install the OS from the USB (video here - note, this WILL DESTROY ANY DATA ON THE DISK).
• If this does not find any disk where to install the OS, the disk is broken (possible as it's really old) and you have to replace it (see here and here) before installing the OS
• This won't run Windows 11, Windows 10 goes unsupported in a few months, consider installing a Linux distro instead (same procedure, create a bootable USB and install)