Hi Plantman,
Welcome to the forums!
If you have a PC running XP then you'll be fine to watch your HD download purchase...
You can also stream your purchase online using NEDweb player on your PC, iPhone and iPad:
- Click on the "Watch Tutorials" button in the top right of the page.
Definitely contact our Support team:
http://www.macprovideo.com/support/
who will be able to help you out with this issue further.
Please bear in mind that our Support team work Mon-Fri.
Best
Rounik