Try first connecting the firewirecable to your pc, then connect the cable to your camera, turn on the camera and then turn on your pc.
If you do it in that order it should work, if it doesn't try connecting your camera onto another pc, preferably using another firewirecable.
If that doesn't work either the problem is with the camera and it has to be checked.
If it does work then you have to look further at your own pc:
try another cable, if that doesn't make a difference try another firewire card (You don't have to worry about drivers) and last thing you can do is reinstall windows. (Isn't videoediting fun?

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