I'd actually go for a 1m (3 foot) cable. I don't really need anything longer at the computer.
However, on set I've used 25 foot cables without any problems.
I couldnt find 3foot so I went with 1.5m (5-6foot)
[moved to hardware forum]
In using the firewire port, you also want to ensure that the 1394 controller in Windows is selected to Legacy, because with the default driver, the firewire connection won't work. I had that problem when I tried using my Panny DV-2000 deck with my laptop and the firewire connection had no response. When I changed the 1394 host controller to legacy the deck responded through the FW cable.