If you are using RoR (Ruby on Rails) and Windows to develop you probably ran into this problem. You want to install a Plugin and use it in your application, so you find some tutorial or links anywhere on the big WWW and when you copy/paste the links they do not work and you get an error message telling you that this is not an executable file. Much like this:
C:\repository\ruby\project>script\plugin install git://github.com/dougal/daemon_generator.git
'script\plugin' is not recognized as an internal or external command, operable program or batch file.