If you use avalaunch then here is an excellent way to get video back say if someone fucks with your settings.
Get enigmah-x video switch, extract the xISO, put in on your xbox somewhere in a folder. Then in the quickstart option, make the right trigger "quicklaunch" enigmah-x video switch.
Now if you ever need to recover, turn your xbox on while holding the right trigger for about a minute (this will launch the video switch) the select A (PAL) or B (NTSC), then turn your xbox off then back on and it should work!