Railroady on windows

Hi!
I try to generate uml class diagrams for my rails app, the problem is when I run rake diagram:all I have an error

Generating C:/Users/Maki/Desktop/prinz_gustos/doc/models_complete.svg
railroady -ilamM | dot -Tsvg > C:/Users/Maki/Desktop/prinz_gustos/doc/models_complete.svg
'dot' is not recognized as an internal or external command,
operable program or batch file.
rake aborted!
Command failed with status (255): [railroady -ilamM | dot -Tsvg > C:/Users/Ma...]

(See full trace by running task with --trace)

I think the problem is that I'm on windows, anybody knows how to solve it?