Once I fire up Rubywin, and then invoke _R_uby _I_rb from the 
menu, I get the message:

 D:\PROGRAMS\DX4\RUBY\BIN\rwlib\rwirb.rb: No such file or 
directory -- 
./D:\PROGRAMS\DX4\RUBY\BIN\rwlib\rwirb.rb(LoadError)



    from D:\PROGRAMS\DX4\RUBY\BIN\rwlib\rwirb.rb

    from D:\PROGRAMS\DX4\RUBY\BIN\rwlib\rwirb.rb:0

I then ensured the folder was added to my PC's %path% 
variable... but got the same message.

I then tried _F_ile _O_pen -ing
D:\PROGRAMS\DX4\RUBY\BIN\rwlib\rwirb.rb
and then _R_uby _R_un file... but got the same message.

Is there something really obvious I'm missing here?

(I haven't developed since the days of dBase on CP/M and 
MP/M, so please go easy on the assumed knowledge).

Thanks in anticipation,
Euan