tcltk and BWidget are needed. The "BWidget" is not included in the minimal Tcl/TK package of R. You can download it at http://www.activestate.com/Products/ActiveTcl/ or at maintainer's homepage (see DESCRIPTION file). Once BWidget has been installed a $TCL_LIBRARY$ environment variable must be set to the Tcl library path, /usr/lib/tcl; C:\Tcl\lib\tcl8.4, and to a non-empty string, e.g. "Yes", a $MY_TCLTK$ environment variable. If after this there are still problems try loading BWidget from an R workspace: tclRequire("BWidget"), after changing the working directory to the folder where BWidget was extracted, it is suggested /usr/lib/BWidget, C:\Program Files\Tcl\lib.