Solved. Putting vu2.3 into c:\Tcl\lib\ and setting env: set TCLLIBPATH=c:/Tcl/lib (forward slashes!) works. Details: RubyInstaller-Forum, 2012-01-27, "Windows RubyInstaller 1.8.7: Installing missing TCL/TK packages?": http://groups.google.com/group/rubyinstaller/browse_thread/thread/332c4664b8a52eb8# Axel -- Posted via http://www.ruby-forum.com/.