Where did you get it? Contact the seller....
Is the hard drive spinning?
If you're not concerned about warranty, open her up and check for lose ide and/or power cables.
There are some special 50x codes that test and initialize a drive... I'll have to get them from home.
You could plug the drive into a pc and run the vendor diagnostics (BUT DON'T REFORMAT IT - some sectors contain box critical information).
If the hard drive is ok, your're probably sol. If the hard drive is bad your just 'mostly' sol.
It's possible to replace it, but DEFINATELY NOT FOR THE FAINT OF HEART:
http://groups.yahoo.com/group/dishmod/ (read, read, read - then, read some more)