Nnexxus: Well, that's just not true. Many linux distros provide a bootable ISO that you can write to a USB key. Afterward, you just plug in the key, reboot the computer, and there you are. No hard drive required, all data (OS + documents) are stored on your key, you can even physically unplug the hard drive if you wish. No real limitations, only a slightly less reactive OS due to the USB transfer rate.