Ok everybody, I have found a 100% free way to get that pesky 2 track audio down into just 1. Its kinda complicated, and you may have to download a program if you dont already have it. Its called audacity. Just google it.
First make a copy you video first just in case.
So you go into the latest version 1.3.12 i think(dont forget to download the LAME mp3 and ffmpeg with it (its easy, instructions are on audacity website)) and open up your video .avi file. It should take a minute and automatically convert it to just audio( no video). Then you export it into an mp3 file (thats why you need LAME mp3 encoder library) when you do that, it should tell you that it will mix the two tracks into one message or something. Save it somewhere you will remember. That is the audio part.

Now go into windows movie maker, and put your video file (thats why you made a copy) into the timeline like you would normal. Then click the plus sign next to "video" in the timeline, and RIGHT click on the audio portion. Click mute, so the audio to the original video will be muted. Then import the audio you did with audacity and put that into the audio portion in the timeline. Then all you need to do is publish to this computer and there you go. Completely free, and the audio is one track. Works with youtube (tested).

Wow, that looks like a lot. It is REALLY REALLY simple, trust me it takes me about 5 minutes at most. I just wanted to explain a lot.
I found this out completely by myself, too. I feel very accomplished. I hope this helps!!