(RubyScript2Exe is a utility that creates a single binary file containing everything needed to run a ruby program, including Ruby itself. The following are instructions from Mark Felt, who was kind enough to get it working, with my notes in italics.)

1. Use 'rubyscript2exe' to create an executable (still needs a tweak!) (Execute rubyscript2exe Mondrian.rbw and close Mondrian when it runs)
2. Copy the executable to a new directory.
3. Extract the files from the executable. (I used Mondrian.exe --eee-justextract)
4. _Most Important_: Copy the 'icons' & 'images' from the Mondrian IDE to the extracted 'apps' directory.
5. Edit the extracted 'apps.eee' file. (My file was just 'app.eee')
6. Remove these two lines: 'd apps' & 'f apps/Mondrian.rbw' (Again, for me it was just 'app' in all cases.)
7. Add 'r apps' somewhere _before_ the last line in 'apps.eee' (i.e. _DO NOT_ add it as the last line!!!) (Just 'app' again.)
8. In the directory you extracted the files from the created executable, run: 'eee apps.eee Mondrian'. (I had success with eeew app.eee Mondrian.exe Mondrian_new.exe.)

You should now have a new executable which is completely self contained and should work anywhere. (I tested my copy on a minimalistic copy of Windows XP.)