How can I track if my visitors are looking at the videos on my sales page (eg clicking the play button) and also track how much of the video they watch?
I've got video on my sales page but I don't know if anyone watches it, and therefore I can't see how it affects conversions.
If the video was added after you already had sales, you should have seen a difference in your sales numbers. If there was no change, then it's not helping. If the video was there from the beginning, you can use split testing to see if it affects anything. Some things you could check: with and without it, try changing the lead-in text, try changing the position of the video on the page.
Right now you have it as a flash movie. If you had the video on YouTube, you can still embed it in your page but you'd get a lot of people viewing on YouTube too. You could put it on Google Video as well.
Some sites like sitesell are getting a lot higher conversion rates now that they've added video. But some affiliates with a lot of traffic got the clicks to view the video and had no conversions. What was missing was the context. With good pre-selling text leading up to the video, much better conversions result. Their main page has video now. Check it out: http://www.sitesell.com/ya_think.html