There's a three minute trailer for the Hammers of Fate expansion on the official Might and Magic portal. Download it directly from here, or view a lower resolution version in the forums.

A short cutscene introducing the protagonists of the campaigns is followed by a series of gameplay sequences. We can see various dwarven units in action, get a first glimpse at a Fortress town and visit the new and, allow me to say it, really cool snow environment. Heroes Of Might & Magic 5: Hammers Of Fate will be out in two weeks, according to several retailers.