i readed you need to go to the media player to load the autoexec then you can add rom into a umcdr cd or into the usb key.
if it says no files found and/or the usb key work light stay on this means it's not compatible with a armax. for example mine (that work with ps2os) don't work with armax
ps2os betatester, ps2tools codev, hdldump frontend dev
6 sony mc w/ps2os 0.2.4, hdl, ps2rmp1.50,ps2mp3...
na+hd maxtor diamondmax 7200 120GB
PS2 SCPH-30004R V6 ÐM$3 V2 firm 2.4 B.4
PS2 SCPH-50003 V9 ÐM$4 PRO firm toxic os 0.1