Someone needs to tell this kid about Portable Apps. They are programs that run off a USB drive, so there's no need to install it on any computer. All Open Source (ie free as in beer) and has just about any program one could need including Firefox and Thunderbird.
I know about Portable Apps. We have software to prevent any application from being lauched from a USB drive. They can save data and read data from the drive, but not launch any executables.