Hiya,
I am not an expert but I would say:
Get some testimonials on the page from previous customers, if you have none give away some free copies in exchange for a testimonial.
Put some text links to buy now at regular periods throughout your sales page copy, rather than only having a buy now button right at the very bottom of the page.
Maybe a bigger buy it now button, I have one you can use that converts well, but I cant post a link or image yet, so if you pm me I will send you it.
I would maybe even move the large guarantee certificate to under the sales button not before.
Are you split testing your headline? Always a good idea to try out a few and see which one converts better.
Just a few things I thought of, Sally
