your evox.ini file is on the xbox HD in one of the folders. Look for it and you'll find it. I think it goes in C: if you are using the original xbox HD, i forget.
look for the line "DVDPlayer = "f:\apps\dvd2.0\default.xbe""
and change the stuff in quotes to "C:\xboxdash.xbe" if you are using the MS xbox DVD playback kit. If you are using some other DVD program you will have to set the quotes to point to wherever that program's default.xbe is at.