Why do all hardware producers make up their own key combinations to access the BIOS? I never remember. This time it was an old DELL, that forced me to download the user manual: It is Ctrl+Alt+Enter. I needed to change the boot priority in the BIOS to enable scsi booting. Funnily grub confuses the disks and you manually have to specify the correct root(hd0,1) in the /boot/grub/menu.lst. Grub writes its guess of hard disk order to /boot/grub/device.map, but the guess was wrong in my case.