- Download the alternate install cd image
- Find a usb thumb drive with at least 1GB free (may need more, up to 2GB)
- Download usb-creator, and run it (usb-creator-gtk or usb-creator-kde on Kubuntu)
- In the top box, choose your alternate ISO image. Plug in your usb drive and it should appear in the lower section of the window. Choose the drive (for example, /dev/sdb1) and choose "Discarded on Shutdown".
- Click "Make Startup Disk"