What if your computer crashes just when you need it the most? With no other computer available, you will have to either sit brooding or try to get it running by installing a fresh operating system. Why not carry a portable operating system on a USB drive to cope up with such exigencies?

Portable versions of a number of operating systems are available. Five popular operating systems that can be installed on a USB drive are:

Slax

Slax is a Ubuntu-based operating system packed with all applications that one might need in day-to-day computing. It can be downloaded from the Slax site after customizing it with the desired applications. Installation is quite simple--unzip the archive folder and click on one file. Once installed on your USB, it behaves like a normal operating system. You can install applications, save files, etc. It is also fst enough not to let you feel you are working on a USB drive.
[Slax]

Puppy Linux

Puppy Linux is a small Linux operating system, ideal for use on USB drives. With less than 100MB size, it can be easily loaded on to a USB drive or CD. It comes packaged with necessary applications.
[Puppy Linux]

Damn Small Linux

Damn Small Linux (DSL) was originally designed to see if a Linux could be squeezed into a 50MB CD. The developer did not only succeed in his personal adventure but also created a versatile operating system. It comes equipped with Firefox, instant messaging clients and even a web server.
[Damn Small Linux]

CrunchBang

CrunchBang is a Linux derivative. It is developed from a minimal Ubuntu install and lays emphasis on multimedia functionality. It comes pre-installed with lot of multimedia applications that Ubuntu misses out. It includes Firefox, Pidgin, Skype, Gwibber, Abiword and GIMP. CruchBang is perfect for Windows users who want to get started with Linux as it comes packaged with most tools that one has to install on a fresh Ubuntu system for multimedia and other functionalities.
[CrunchBang]

Portable Ubuntu

Ubuntu is my personal favourite, making the portable version an automatic preference. Ubuntu Live CD or operating system comes with an in-built functionality that can install Ubuntu on a USB drive in two clicks flat. Just pop in a Live CD and restart your computer toboot from CD. If you already have Ubuntu, go to System->Administration and create a USB installation. You can read 10-part Ubuntu series that starts with how to get started with Ubuntu.
[Portable Ubuntu]


Apart from the above, there is Back Track, a security-focused Linux operating system. It is most useful for people who want to troubleshoot or crack passwords, or do anything geeky. It will analyse your entire computer or network and do almost anything for you.

How to install Slax Linux on a USB drive?