They "slayers" version of evox doesn't have the flash menu option. Install the "default" evox.ini file from the standard evox distribution and you'll see it (Settings --> flash bios)
Procedure is to put a folder called "bios" in the same location as evox on the hard drive. In that folder, put the bios you want to flash (Should be 512k for the duox2.. though evox should automatically resize if it isn't). Then reboot the xbox, go to the flash bios menu and select the bios you want to flash. Press Y to flash and wait for the xbox to shut off.
