From what you have posted, I'm going to say Captivate isn't what you want. It sounds like you are wanting to capture a very long presentation using full motion capture. Captivate has made progress in this area, but I'd be surprised if you found it to be acceptable for doing this. Don't get me wrong, Captivate is an awesome tool for what it does. But full motion isn't it!
You might consider TechSmith Camtasia Studio if that's what you are trying to do. If you do this, don't be surprised to discover that even Camtasia Studio isn't able to capture the audio. It's because of a limitation of some sound cards. That's why something called FreeCorder Toolbar was invented.
You would then use FreeCorder to capture the audio while the other application captures the video. Then you would import the resulting audio into the other application and synch it up.
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That's very good info to have. But what is the answer to the original question, is audio recording disabled in the trial version?
If you are using the in-built mic for recording then you have to make sure that the volume of the input device is correctl set. Follow these steps:
1. Right click on the speaker icon in the system tray. Select "Audio Properties".
2. In the Sound and Audio Device properties window goto the "Voice" tab.
3. In the voice Recording section click the "Volume" button.
4. Make sure that the volume for Internal mic is set to its maximum value.
Now try recording using captivate and see whether narration recording works for you.