Thanks guys for your answers.
I'm running FC5 in VMware right now, so my tests might not be that relevant, but I do have another question.
Firstly, at what point in those instructions (http://fedoraproject.org/wiki/RenderingProject/aiglx
) should the new visual affects appear? The instructions end by saying you should add the 'Composite' extension to your xorg.conf file, but then what happens after that? I have re-booted but there is no change.
And my second question was going to be "I still can't find gconf-editor - where is it?" but I've just figured this out: I needed to install it with "yum install gconf-editor".