Have a fresh install of Kubuntu 8.04 Hardy Heron with KDE 3.5.10 from the Live CD. However, I only want the kdecore. May I uninstall everything, except for kdecore--or is there a way to run a minimal install using the full live cd??

I do not want to upgrade to 8.10
I do not want to upgrade KDE neither.

You need at a minimum kdebase and kdelibs for a minimal desktop. Note that this will contain none of the PIM applications ( KMail, Akregator, KNode ) and other applications such as Kate, KMix, etc. will also be missing.