While I have tried several different Linux distributions, the way that I prefer to install another Linux distribution on top of another, is to not just put another installation on top of it but to first prepare the harddrive. To do that, you can boot into a rescue mode and prepare the disk. To use the ext3 filesystem, with the old Linux distribution on partition 2:
# dd if=/dev/zero of=/dev/sda2 bs=1024
# mkfs.ext3 -c /dev/sda2
Then I would reboot with the installation cd and use partition 2 for the installation. You do not want to have parts of the old installation on the harddrive when you try to install a new Linux distribution.
Also with OpenSuse, on an LCD monitor, I found it very helpful to change the monitor resolution to 800x600 with the F3 option before selecting the option to start the installation. Otherwise, my LCD monitor would go blank and it became a problem to complete the installation since the default monitor settings in the installer where not optimal for the LCD. Similarly if you need a driver you can load it at that time too.