EasyCAP Dual sound recording

[Oxymoron28]

I've tried to google this but have no real idea how to word it so I'll try my best with this topic and hopefully get the idea across.

So I have an EasyCAP Capture device which I use for capturing gameplay, it records really well and the sound as well. But I see a lot of people who capture their video and game audio and are able to to an audio voice over at the same time.

I have both Sony Vegas Pro 9.0 and Ulead Video Studio, in Vegas I tried setting up 3 tracks, 1 for video, 1 for game audio and 1 for microphone audio but could only get it to record the microphone and nothing else, and with Ulead Video Studio I can't see an option.

The only other method I can think of is using Audacity to record the voice over and adding them together in the editing part but it'd be hard to sync them up and also hard to set them to record at the same time, so does anyone else have any ideas? or are there any plug ins that can help?

[usually_quiet]

The voice over is likely added later. I suspect they just play back the recording, record their voice-over while watching it, and merge the two audio tracks afterwards.

[Edit] I suppose they could also have recorded their gameplay using one computer while recording the voice-over using a second computer, and merge the two audio tracks afterwards.

[Oxymoron28]

The voice over is likely added later. I suspect they just play back the recording, record their voice-over while watching it, and merge the two audio tracks afterwards.

Some do the commentary afterwards but I know that others do it whilst they film.
(Example: http://www.youtube.com/watch?v=ieZOtxKgI8M)

[usually_quiet]

We were typing at the same time. I added to my previous post.

As far as I know, it is only possible to have one audio input selected at a time. Maybe there is a YouTube video on doing voice-overs, since there seems to be one on every conceivable subject related to recording whatever with an EasyCAP.