XBE dumps can be generated from any Xbox discs you have, using either of these procedures.
Cxbx: Start it, open an XBE, choose menu option "Edit | Dump Xbe Info To... | File..."
Dxbx: Start it, open an XBE, choose menu option "Edit | Dump xbe info to | File"
XdkTracker: Start it, choose menu option "File | Get XDK Info from Xbe"