It's not a BUTTON for HD versus non HD. It's a setting. Eric says he thinks it's the Dish remote, 'options', and that gives you the option to view non HD channels. And, as Louise said, you can just type in the number and it will work. It just doesn't show on the channel guide.

Edited to add---Eric says that the looked it up on the internet, on the Dish website, how to do it...