Ubuntu makes it easier for everyone and with Wubi installer it goes another step in introducing a thing which makes it much more easier for people to install and give Linux a try. More here

So you get to install the Ubuntu or Kubuntu linux in your system like a piece of cake and none of your partition or boot record gets disturbed. You reboot and start testing and learning the Ubuntu Linux as much as you want and if anything goes wrong you can simply uninstall it. Once uninstalled the folder where the Ubuntu partition is will be deleted and your NTFS partition will stay intact. No harm done.