I can assist with OS installation. What operating system are you trying to install?
I can assist with OS installation. What operating system are you trying to install?
You're trying to create a bootable USB for Windows 8.1 from a disc, but Rufus isn't showing an ISO file. It seems the instructions are pointing you toward an ISO, which isn't available in your current setup. You might need to use another tool like Windows Media Creation Tool or a similar utility that can generate an ISO from your Windows installation media.
Download ImgBurn and apply it to create an ISO of your disk: http://www.imgburn.com/. Be mindful of the ads it displays, as they may attempt installation. Try to avoid them during setup. You should be able to learn how to generate an ISO file from a disk; if not, search for guidance or ask here. After creating the ISO, you can use Rufus to transfer it onto a USB drive. An ISO is essentially a complete disk image that exists digitally, not physically on the device, but can replicate another identical disk. I hope this assists you.