Installing over Ubuntu CNC distro

I have been using the LinuxCNC distro for a year or two now, and the antique laptop that I have been using for it is failing. First the display, now the keyboard. Fortunately the Compaq NC6000s are readily available used and cheaply. But when I received it, I overwrote the Windows XP OS withe the Ubuntu CNC distro that came with my Sherline mill. How do I install the LinuxCNC distro on my DVD over the Ubuntu distro?

It is very simple if you want to completely replace it. Simply choose to have the installation program reformat the harddrive and everything on it will be removed and replaced with the new installation. I believe that is the default setting. (be sure there isn't anything on there you might need to save first.)