Thanks for the tip. Unfortunately, still no success.
I burned the .iso-file from the BIOS-CD folder on a dvd and put it in the Z800. However, it seems that nothing is being done with it. Still no display. I also created a bootable USB drive and put the binary (rom.bin from the .cab as well as the 7G5_0360.bin ) in the root. This does not seem to trigger any reaction in the Z800.
Nevertheless, I am still able to restart the PC via pressing CTRL+ALT+DELETE on the keyboard. I guess its the little things we should be happy about.
Did I do anything wrong? Are there any alternatives?