Okay, mainstream support for Windows 8.1 ended way back in January 2018. Windows 7 support was extended to to January 2020. It seems completely backwards, but that's how Microsoft has done things. Unfortunately I'm not sure if the latest versions of LaunchBox/Big Box will work on Windows 8.1. I think they will in theory, but you probably will get subpar performance compared to Windows 10, and it might be tricky to get all the prerequisites installed correctly. So, to be honest, I would highly recommend upgrading to Windows 10 at this point.