SteamOS Unofficial ISO is a custom ISO image built over SteamOSInstaller.zip archive. It provides standard ISO image so it can be burnt to blank DVD disk, copied to USB stick or tested on a virtual machine. The ISO image is an unofficial, not provided by Valve but fully compatible with the original system. Means no modifications, no changes, just pure SteamOSInstaller inside the ISO image. It is targeted to 64 bit machines with UEFI motherboard.