This was the original hack, exploiting a bootloader vulnerability. It is superior to RGH (instant boot times), but it only works on very old "Dashboards" (versions 2.0.7371 or lower). Unless you have a console from 2009 that was never updated, JTAG is unavailable.
The Xbox 360 store is now closed. Many games are delisted (e.g., Forza Horizon 1 DLC, OutRun Online Arcade ). For preservation, the ROM community views these ISOs as necessary to save gaming history. xbox 360 roms iso work