Black Box Voting has a step by step explanation, with detailed pictures, of how to alter a Diebold electronic voting machine in four minutes flat, including defeating two "security" features. The process is undetectable, and you can easily alter vote counts in the machine, and it would be impossible to trace because the machine does not provide auditable paper records.
Your tax dollars at work. Hanging chads are starting to look pretty good, since you can at least see them.