Most likely your Xbox is booting the dash from the xboxdash.xbe file in the C drive. When the Xbox boots normally, that is the file it looks for. Using FTP, copy your avalaunch files to the Xbox C drive. Rename xboxdash.xbe to old_xboxdash.xbe then rename your avalaunch.xbe file to xboxdash.xbe. Reboot the Xbox and it should boot to avalaunch.
Keep in mind that if this doesn't work you will need another way to get into the Xbox. Make sure you have a game save exploit on the Xbox. To check it out, boot the game used to do the mod. If the guy doesn't remember what game he used, go to the MS Dash and look at the game saves in there. It will list under Mech Assault - Run Linux for example. Boot that game and make sure you can see the exploit.
If all else fails and you can't do that, you will have to hotwswap. These are warnings just to let you know that things can go wrong and you need to be prepared to fix them. If the DVD doesn't eject, take out a paper clip and straighten it out. There is a hole on the right side of the DVD drive. Use the paper clip to press in on a lever in there. It will make the tray come out manually.
