Taka, just record it using camtasia and then use a different audio software to record yourself, and put it as a soundtrack to the movie.
that was the plan, I've decided now that I'll use the built in recording function to get a screenshot of each frame, that way even if I do experience some slow down, there is none recorded, and I have full control over every pixel of every frame.
Originally I thought I would have to export all those frames as a giant gif, lose a bit of colour detail, then convert to a movie file, but I've discovered I can import the frames in windows movie maker, and save it as a movie file - Cutting out the middle man

The only annoying thing is the quickest speed it allows for each frame is 0.1 seconds, but once I convert it to a movie I can easily speed it up
