I haven't tried this myself yet but plug the video out from the RCA on your friends camcorder into the analogue in on your digital cam (that is assuming your digital cam has that facility) and run the audio into the sound card, possibly using RCA to a 3.5mm plug then take the firewire cable and run it from the digital camcorder and connect it to the firewire in socket on your computer. That way, you will pass the analogue video signal from your friends cam through your digital cam and have it converted from analogue to digital and then on into the computer for capture. Your software should be able to pick up your digital cam, I know it's a bit fiddly but I would stay away from those USB jobs as the quality is terrible.

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Better than a poke in the eye with a pointy stick any day...