but there is no option to purchase the original Windows 8.1 software from HP, for your model.
However, on that same page, is "HP Support Assistant" ...
Type: Software-Solutions Version: 22.214.171.124 Rev.A Operating systems: Windows 8.1 (64-bit) Release date: Feb 17, 2016 File name: sp74656.exe (39.4 MB)
This package provides the HP Support Assistant software for the supported notebook models running a supported operating system. HP Support Assistant enables HP customers to discover, maintain, and troubleshoot issues with their computers. It also enables customers to contact HP to receive assistance.
Through this software, it may download the "missing" software.
Also on that page are downloadable versions of the original "Cyberlink" suite of software.