A standard .iso file is a sector-by-sector copy of a disc. If you rip an Xbox game using a standard DVD drive and create a raw ISO, you will get a file. However, the original Xbox BIOS looks for a specific "Xbox DVD-ROM" volume descriptor and a hidden security sector (the Xbox’s copy protection). A standard ISO strips away this "Redump" specific data, resulting in a file emulators and modded consoles refuse to boot.
As of 2026, the original Xbox is over 20 years old. The XISO format remains the gold standard for preservation because: Xbox Xiso Roms
Use Xbox Image Browser (Windows) or extract-xiso (Linux/macOS command line): A standard