For the purposes of this list, a portable application is software that can be used from portable storage devices such as USB flash drives, digital audio players, PDAs[1] or external hard drives. To be considered for inclusion, an application must be executable on multiple computers from removable storage without installation, and without writing settings or data onto a computer's non-removable storage. This includes modified portable versions of non-portable applications.
mIRCNote: There is a U3 version of mIRC that can be installed on U3 drives. The original application is portable, leaving behind only the license key in the registry. (This may not be true with the newer versions that are Vista-compatible, as their default user data area was changed to the user's application data folder.) Since v3.1, it can be started from a command line using the -portable switch to use settings, DLLs, and license keys that are stored in the same folder as mirc.exe.
WinRAR, Portable version for Windows, still requires having a license for a regular version of WinRAR. The version number for WinRAR Unplugged is 3.8.0.1, while the latest WinRAR for Windows version is 4.11