If you have a Bios disc of EvoX (Which should ONLY contain the BIOS.BIN file, and the DUMMY.BIN file)
Then you have to go to the FlashBios screen.
(remember to enable the chip quickly press power and you will see the "X" on your switch as BLUE, NOT red.)
Once you are in FlashBios then select Flash from disc, and insert your Bios CD.
IF that continues to cause a problem you MAY have fubarred the CD, and try the HTTP flash instead.
Having the flubber animation screen with the "EvoX" emblem attached lets you know that you are using their hacked bios that will allow the Xbox to run things like Slayers 2.6 boot disc etc.
Without one of those tainted screens you are simply using the nomral Xbox which will NOT allow you to simply boot any file.
****NOTE****
Make SURE when you flash the bios that you have the proper banks selected when you install your bios! THe EvoX Bios is 256K, so I would suggest one of the higher banks that don't contain the FlashBios ver that you need.
If you have a 1.6 (not 1.6B) then flash it to bank 8, you don't use the flashbios that is there anyway.
If you have any other version then (1.0,1.1,1.2,1.3,1.4,1.5,1.6b)
Flash Evox to one of the first 4 banks as you would do best to use flashbios 3.0.3.
ps, WHY use EvoX bios? You will notice once you get the EvoX dash in there that ALOT of options are greyed out. Go to the usual place and get the X3 Bios! (1MB)