Did you use an SD card not bigger than 2gb ?
Does the SD card have any disk name ?
Wait for this as last option
Try to put this two 7934 rom files winceimg in the root of sd card ans see what happen .
Must power off/on with reset key pressed to read files from SD
EDIT 2 option
Before doing above , i found a 7914 flash disk image , lookink inside the .exe i presume at boot it will start this file \SDMMC Disk\becker.exe .
Try to put total commander with the above name becker.exe on the \ root of the SD or inside a folder called "SDMCC Disk" on the SD or
try to give "SDMCC Disk" as disk name of the SD .
EDIT 1 option
I've read that when the 7914 display the becker logo you can press the 4 corner of the screen clockwise starting with the left top and it will run an hidden menu ( FACTORY TEST MENU ) where you can select ( Run Navigation ) , try if it works .