It never ceases to disappoint me how many people just don't seem to get this.
Machiavelli was not medieval. Machiavelli wrote about many medieval Rulers, however, as well as various general principals applicable from the earliest days of the Romans to the current day in addition to early modern Rulers and the like.
There is also no conclusive evidence that the Prince was a satire. I think it's more instructive to look at when in life he wrote the Prince as opposed to, say, the Discourses on Livy. He wrote the former later in life, and he was always a partisan of a united Italy. It's not terribly hard to envision a man who felt that a united Italian Republic was not practical after decades of experience in politics, and thought that a united Italy was more important than his republican principles.
Besides, even if it were a satire, it's very, very good advice for would be and current Rulers, as various Holy Roman Emperors and the Founding Fathers of the United States found (though, of course, the latter were more interested in the Discourses on Livy).
And I would like to finish with this: Just because you believe in something, doesn't mean you can't use it as a tool for other ends.
