FANTASTIC! It´s working fine with the 80-GB-HDD!!!
Only the "IDE Auto-Detection" doesn´t work any more. It hang up and freezes during the Auto-Detecting of Primary Master. All what´s displayed in the red box is a lonely "2".
So I decided to set every "Type" of the HDD to "auto" in Standart CMOS Setup.
And now it worked!
Thank you very, very much!!!
Michael