DV in will work when you connect by firewire but you need the camcorder to be on Play ( or VCR) rather than Rec, camera
As it is
DV in you can only record a DV AVI on the PC to tape, not an other video format. It is generally so you can record your edited video back to tape but you can actually put any video on it as long as it is a DV AVI
With Camcorders which have
AV-in you could generally record any video as long as it was being output as video
With DV in you will generally see the video playing on the camcorders LCD
You can activate recording via software or on the camcorder it self ( should say how). with many you need the remote control to do it.
Try doing it with this
http://windv.mourek.cz/