Access the DVR Events menu. NOTE: DVR Events can be accessed one of two ways: Press the DVR or PVR button on the remote. Press the Menu button on the remote Select My Recordings for models: 501, 508 Select DISH on Demand then My Recordings for models: 510 and 612 Select Preferences then My Recordings for models: 522, 622, 625, 722, and 942 Select TV Listing then DVR Lists for models: 721 and 921 Once on DVR Events menu, Highlight and select the event to be deleted. Highlight and select Erase or Delete. Select Yes on the pop up screen that confirms the deleting of the event. Note: If the receiver is locked, it will prompt to enter the password.
I assume you mean the entries for things you have already watched and deleted. No they cannot be removed manually. I think they remain for a week. One purpose is to prevent duplicate re-recordings of things you have just watched.