how can i install and uninstall the ubuntu system

Installing it is very easy, download the .iso image or order a free CD, pop it into your CD drive and boot from it (if you omputer doesn't auto-start on CDs then you should change that in your Bios). Then just follow the installation instructions provided by the installer (overall they are very easy and if you don't udnerstand something you can post it here on launchpad).

Uninstalling it isn't as simple though, as linux installs the grub boot loader, which makes it easy to choose between different OS systems (like XP and ubuntu in this case) and this program will be executed every time your computer starts from it's harddrive. So if you have deleted the ubuntu partition this program will fail and you can't start then, the easiest solution is, for as far as I know, to use youw windows install CD to fix that, it should have some kind of solution for this problem according to a lot of people. But as I don't use windows (only like once in a month to play a game or at school) I don't have an idea how that'll work.

But I don't see why you would like to uninstall it, first of all you have the live CD, so you can try ubuntu before you install it. And if you like it a bit, believe me, your love ill grow very fast ;) :D

PS. Also a good place to search for some information is your LoCo-group, these are people from your own country and/or state that give information, support, have discussions and I even give presentations at school as LoCo of ubuntu-be. Just search for it (most of the time it's ubuntu- and then your country code, like in the domain names ;) )