Write-ups · Root cause · 6 Sept 2026
Why xemu says "Please insert an Xbox disc" to a perfectly good image
Disc images dumped from my own original Xbox games would not boot in the emulator. The images were fine. They were the wrong kind of fine.
- What they said
- The emulator rejected every disc image I dumped.
- What it was
- Full dumps put the game partition at 0x18310000. The emulator reads 0x10000.
Symptom
I dumped my old Xbox discs and pointed the xemu emulator at the ISO files. Every one of them gave the console's own error: "Please insert an Xbox disc". The files were not corrupt, and they were all exactly 7,825,162,240 bytes.
Reading the bytes
That identical size was the clue. A full dump of an Xbox disc contains two things: a small standard DVD-Video partition that tells an ordinary DVD player "this is a game disc", followed by the real game partition in Microsoft's XDVDFS format. The game partition's magic string, MICROSOFT*XBOX*MEDIA, sits at offset 0x18310000 in a full dump.
xemu expects an image of the game partition only, where that string is at offset 0x10000. Given a full dump it looks there, finds the DVD-Video data instead, and correctly reports that this is not an Xbox disc.
dd if=game.iso bs=65536 skip=6193 count=1 | grep -a 'MICROSOFT\*XBOX\*MEDIA' # full dump
dd if=game.iso bs=65536 skip=1 count=1 | grep -a 'MICROSOFT\*XBOX\*MEDIA' # game partition only
Fix
extract-xiso -r rewrites a full dump as a game-partition image. It is not packaged for my distribution and the server has no compiler, so I built it in a throwaway container and copied the binary out.
Making it not my problem again
My intake script now identifies every image by its magic bytes and size, not by its file extension. PlayStation 2 and Xbox images both arrive as .iso and have to go to different places. Full Xbox dumps are converted on the way in. Archives that contain a folder named something.iso are handled too, because one of mine did.
What I took from it
The error message was true. The disc really was not what the emulator considers an Xbox disc. When a tool rejects input that looks valid, I open the input in a hex viewer before I open the tool's issue tracker.