Burn your CD or create a USB drive : Linux

Ubuntu

1. Insert a USB stick with at least 2GB of free space
2. In the main menu, go to System > Administration and open 'Startup Disk Creator'

3. Click 'Other' to choose the downloaded ISO file

4. Select the file and click 'Open'

5. Select the USB stick in the bottom box and click 'Make Startup Disk'
6. That's it! When the process completes, you'll be ready to restart your computer and begin installing Ubuntu.

copy and paste from : http://www.ubuntu.com/desktop/get-ubuntu/download