Something is wrong with your configuration in the /etc/X11/xorg.conf. That is not a big issue though but often very difficult for the newbies to come out without frustration. What version of KDE are you using, KDE 4 ?, that is another thing if your laptop is slow.
Meantime for an easy start you can for a while install another Ubuntu derivative which is more friendly than the original Ubuntu. Try Linux Mint 11, download an image here
, burn into a DVD and install. There is lesser chance you will face the same problem. Choose the gnome version of Mint 11 (katya), but do not (never) yet the Mint 12 version because of some known problems.
Hope it helps.