Recently I gave some portable apps a try. A portable applications is a computer program that does not require an installation. Just unzip and execute. According the portableapps.com
Why I like Portable Apps? First, That was one thing I always liked about Eclipse. “Download, unzip and run.”
If you want to backup your system.
For example, Open Office.
Some applications that call themselves portable still require an installation. Afterwards they can be copied around.
One good site for portable applications is http://portableapps.com/ which provides portable ports of famous Open Source applications like Firefox, Open Office and many more.
There are a lot of other sites providing portable applications. However, not all of these “portable” versions are portable For example, I tried a portable version of Foxit PDF reader. The version was portable in the sense that you can start it without installation. But it stored some data (e.g. recent files) in the registry.