I have been able to access an original using the doubledash, but it should work with any of the audio hacks as far as I understand them.
Startup - you should get the normal dashboard. Then insert the disk.
Wait for a couple of seconds (like 3 or 4) and before the game is launched, start the hack (with dd which is what I use you select the Xbox Live! tab)
It will freak out for a second. The screen went black, then flashed the original dash for a second then I got avalaunch (the dash I use.)
Disk is recognized as a game, not a DVD. Just finished copying Halo as a test.
As far as signing xbe's on the xbox, I am working on it. I have already gotten xbedump to run on the xbox, but it hangs (using a custom compiled version for DOS and bochs.) I am currently looking into using the xbox-linux live CD to do it, but its not completely finished yet. I will let the scene know if I have any success.
