Janos,
You use WinSCP to transfer files between radio and Windows computer. I first loaded 1.1.9 and updated the base firmware to 1.1.8, then copied the x6100_ui_v100 file to my computer, then load 1.1.7 to the radio and copy the x6100ui file from the computer back to the radio, replacing the 1.1.7 version that was there. The x6100ui file is located at /usr/app_qt. You can see how to use WinSCP in the YouTube video here:
Gary
W9TD
Gary