The WT1200LE has no (accessible?) BIOS. There are no boot options that can be set. However I did find this explanation of the boot process:
The first file that the Thin Appliance looks for in the wnos directory is an update to the boot code in the file UTC_b512. If this file exists and it has a different internally encoded version number than the image currently in flash memory, depending on the wnos.ini file AutoLoad setting the Thin Appliance will load this image into flash and reboot. If the UTC_b512 file either is absent or has the same version as the image in flash memory, the Thin Appliance will check for a file named UTC_wnos. This is essentially the same type of file as UTC_b512, except that it is used to test software images (e.g., to check a new release before installing it) by running the operating system from RAM. If this file exists and has a different internal version number than the version in the Thin Appliance's flash memory, depending on the wnos.ini file AUTOLOAD setting the unit will read this image to RAM and boot from it (the image in flash memory is not disturbed). To prevent an infinite loop in the boot process, the UTC_wnos RAM image does not repeat the checks for UTC_b512 or UTC_wnos.
I guess this is looking in the directory that is set up under the Servers tab on the Network Setup screen.
The WT1200LE runs Wyse's WTOS (Wyse Thin Operating System).
Any comments? email me. Last update June 2011