I also tried video=1280x1024
Try
Code:
screen=1280x1024
I also tried replacing the entire 7.0.5 isolinux directory with the one from 6.7.1.
If you replace the Linux kernel of Knoppix 7.0.5 with an older one you also need the kernel modules included in the huge KNOPPIX file of the old Knoppix.
I would like to configure 7.0.5 to boot up in 1280x1024 mode on the DVI monitor.
Knoppix comes with a utility called ARandR in the 'Preferences' menu. How many output devices are identified by this program?

I think you have to create a special configuration file /etc/X11/xorg.conf which describes the default monitor.

There should be a log file /var/log/Xorg.0.log with a line describing the driver used by the Xserver. If you know the name of the driver you can find out which options it provides to define the default output device.