The mass-production and sale of USB pen drives (key drives/flash drives) and the almost simultaneous emergence of Live-CD distributions of Linux like Knoppix have now made it possible to carry your entire operating system in your pocket in a pen drive. On the computer you want to work on, change the default boot option to boot-from-USB-device (all Pentium 4 based motherboards have this option in the BIOS) and boot up – you have your OS booting up from your pen drive. Do your work in your operating system, shutdown, change the boot up option back to floppydisk/harddisk and the computer is restored – howz that for Plug and Play!
To catch up with the pen drive technology and terminology I suggest that you have a look at the answers.com page for USB drive. The claim is that even if you dip your drive with your data into a cup of hot coffee, you can still recover your data as you would normally! Once written, the data, says the specification will stay inside for 10 years! Simply amazing!