I am trying to install Ubuntu on my iMac 17", but when it asks what I want to do, I can't install Ubuntu alongside Mac OS X 10.6.8; all it says is just to replace OSX with Ubuntu. What can I do?
You need to create a partition for Ubuntu first. The simplest method is to use Disk Utility to resize the Mac OS X partition and leave the rest as 'Free Space'. When you run through the Ubuntu installer, it will then give you the option of installing alongside Mac OS X and will find the 'Free Space'.