DirectShow Driver

At my production company we have just purchased Avid
Express 3.5 (and upgrading to Express Pro). We have the
software and we are trying to capture all of our video
and audio through a firewire connection. For some reason
every prompt that comes up when we connect the deck to
the cpu says that we need to get the DirectShow driver.
To my surprise, I can't seem to find it and the Avid
people have not lead me in a positive direction. If
someone knows where to get this or can shed any other
light on this subject please don't hesitate to respond.
Thanks