Did you buy PowerDVD from Cyberlink store?
If Yes:
To re-download software you have already purchased, you will need to go to your order information page and press the re-download button. To view your order please visit Cyberlink Member Zone and click on ‘Check Order Status.
Looks like you can't exchange a download for the actual product. I found this from Store support page:
Unfortunately, we are unable to exchange a downloadable product for a physical product that you have already purchased. Please place a separate order for the physical product.
Your best bet is to contact Cyberlink support.