From NSIS Wiki
This plug-in is intended to be used in scripts for "portable apps". It finds the first removable drive in the system, and it can also find all removable drives. This can be used to validate the installation and calculate a decent default installation directory.
A realistic example script is also included, which uses the multi-language features of the MUI.
To use, the .DLL file should be copied to the NSIS Plug-ins directory, as always.
The source code is very simple, and is included as a Visual C++ "solution".
GetFirstRemovable.zip (136 KB)