Oops; sorry I think this should be:
Code:
 image=/dev/hda1/boot/isolinux/linux24
and 
 initrd=/dev/hda1/boot/isolinux/minirt24.gz
not
Code:
 image=/mnt/hda1/boot/isolinux/linux24

 initrd=/mnt/hda1/boot/isolinux/minirt24.gz