Didn't try that yet, but this question has come into my mind. Is there a way to use the camcorder via firewire as a substitude for mikrophone? What settings do I have to arrange?
You are better off to take the Camcorder to a quiet place and do your voice overs there. Once done, use your sound card's line in and Sound Forge Studio 6 (believe it comes with Vegas) or Sound FOrge 6 to record directly to your hard drive. This makes your file sizes much more manageable. If you record VOs by your PC you ar going to pick up machine noise. The other option is to buy a good mic, such as a Shure SM57 and record to your hard drive via the sound card's mic in. The high end unidirectional mics are less prone to picking up the sound of your PCs fans.