FC4 Test 3 is scheduled to come out today. Currently I have FC4 Test 2 installed. I was wondering how could I just do a harddrive update instead of burning a DVD again? I'm sure this has been asked before. As far as I know you can mount the ISO image on your harddrive. But my question is do I still need to boot from a boot disk or something and select the harddrive as my install media? Or can I update it from Linux directly? Either through yum or up2date?

your research topic to do this is

" YUM "

good luck,

update :- http://www.fedorafaq.org/#installsoftware

So all I have to do when FC4 Test 3 comes out is say ??

from what I can see, you need to modify yum so that the base packages are installed from the FC4t3 os folder, instead of the other one.
I don't really know... the repo I use is frozen for updates, so I can't do jack.

edit: "update" changed to "modify" for better wording.