When I purchased my laptop from Dell in 2006, I had the option to buy the laptop with hard drive of between 60GB and 120GB. I decided on 80GB to keep the weight down. The laptop is almost 3 years old and the 80GB hard-drive has 40GB of free space left. Upgrading to 100GB or 120GB is a solution - but an expensive one - so I decided to use a portable device to store some of my data. Also, I decided to start using portable applications instead of installing on my laptop, which saves some addition disk space.
Portable applications are handy not only to reduce disk use, but also if you have more than one computer or if you need to fix somebody else's computer.
Below are the best portable security tools.