There isn't anything built in to InstallScript for this, however the documentation for the underlying Windows API call (GetDriveType) has some suggestions to use another API (SetupDiGetDeviceRegistryProperty). See http://msdn.microsoft.com/en-us/library/aa364939(VS.85).aspx to start your research. Note that calling this function from InstallScript may not be easy, so it may be more efficient to create your own C++ DLL which wraps the information you want more directly, and call into that DLL instead.
