In recent years, the term "portable" has quickly come to be associated with apps that you run off a USB memory stick. However, to me, "portable" has always meant that I could easily move apps from one machine to another without too much incovenience. In fact, in the earlier days, I had my portable apps in a separate partition on the harddisk so that when I reinstall or upgrade Windows, I didn't have to reinstall/reconfigure my favorite apps. So in my mind at that time, portablity didn't involve a removable storage device at all. Portable apps are nice because I can easily pass them to a colleague or friend ("Hey, try out this latest version of Firefox with my favorite addons!"), or help out friends when they run into problems with their PCs (eg. file recovery, network diagnosis). I can upgrade to a newer machine and have my favorite apps up and running in no time, instead of having to spend the entire day swapping CDs and reinstalling/reconfiguring apps that I need. This really made my computing life better.