I have installed as primary OS windows XP sp3. Would like to have too ubuntu 12.04 or 11.10 but will be more benefit for me to run from a CD. It's mean i like to install ubuntu not in the hard disk but in a CD. Can I do this? and how? Thanks!
You can, but you won't be able to save any data. If you want a portable installation that you can save data on, you can use a USB drive.
To install ubuntu on a CD, follow the directions here to make an installation CD or USB drive. When you boot from this CD/drive, you will be asked whether you want to "Try Ubuntu" or "Install Ubuntu". Choose "Try Ubuntu" to run Ubuntu from your CD/USB drive.