You could also put CrossDOS into WBStartup, and then it will be run when the machine boots. The DOSDriver (PCx) which is really just a modified MountList entry, controls which device it works on, the FileSystem lives in L, and mfm.device (in DEVS:) replaces trackdisk.device (in the ROM) when it is active. It sounds complex, but isn't really. (I used to use it on my A570 CD drive with an A500+ to read PC CDROMs.)