Snow Leopard Mac OS X cannot start up from this disk

Trying to revive an old 2009 iMac 10,1 and have the following error when trying to do a fresh install of Snow Leopard:

Followed the instructions as per another (closed) discussion: https://discussions.apple.com/thread/3614416

Steps:

Boot from the Snow Leopard DVD and select your language.

Then launch "Disk Utility" from the "Utilities" menu

Select your boot device (the device above the boot volume name)

Select the "Partition" tab,

Then resize the partition by selecting the volume name in the rectangular volume representation and drag the bottom-right corner of it to change its size.

Click "Apply" to change the partition's size.

Revert the change by dragging the same resizing corner back to the bottom, and click "apply."

After this is done, quit out of Disk Utility and try installing Snow Leopard again. Since you are booted from the Snow Leopard DVD you should be able to continue immediately without having to reboot your system.

Unfortunately, I still can't progress...