All IT experts whom i know deny the fact of the presence of a converter from USB - Firewire. Maybe because firewire moves bits faster than USB so there isn't that efficient converter; even if there is such a thing it will slow the INFO transfer greatly. If your desktop didn't come with a FireWire port then purchasing a FireWire card will solve it for you (just like graphic,sound cards, etcc..) For laptops i think that a card can be inserted on those deep rectangular pockets which come from the sides of the laptop, (i have forgotten it's name) will give you a FireWire port.
UPDATE: There isn't a converter for the cable which has the Big FireWire port, however in your case, camcorders have small FireWire ports which are available in the market. By the way they are really CHEAP, just like a normal cable. Maybe the 119$ that is posted includes specialized software for video editing or such stuff. But, if your Camera is digital, and saves on a chip,(not on a tape) then you don't need that one which is posted.
If you didn't notice that type of cable is similar to the one that we use on mobiles.(new ones)