I think I understand now.
Either I use
feisty-desktop-i386.iso (or 64 bit version) herd 4
I change the bios-settings for AGP from 8X to 4X and/or disable fast writing, then install the ubuntu-6.10-desktop-i386.iso (or 64 bit version)
and then install the fix from http://people.ubuntu.com/~kyle/xserver-xorg-video-ati_6.6.2-0ubuntu5_i386.deb (or 64 bit) as a package so I can set the bios to its original AGP settings.
Both live CD’s are starting the graphic shell now.
I downloaded only a week ago the ISO image. Google send me first to this page. I red some of these comments. But I missed that a fix was already available from the beginning of February . I suppose somewhere else a shorter notification is exists.