What is your traffic on your site vs your actual sales like?
This beggs a bit of investigation. Do you find that most people are downloading then purchasing your product from your site, or getting the file from a download hub like cnet then purchasing your product. Why I ask this is I am looking into driving traffic to my site, but if most people are getting their files from hubs then it doesnt make much sense.

I also didnt take this into account recently. A customer had downloaded my app, then had gone streight to my site and purchased a code, he subsequently didnt know what to do with it because he had bypassed my step-by-step explaination in the program itself.