Digital Rights Management (sometimes
Personal Rights Management) is commonly used as a
euphemism to describe defective player/viewer software. Software incorporating DRM technology will exhibit some of the functionality of a correctly-operating application*, but will prevent the user from being able to perform fundamental operations (such as copying, converting, or viewing on another machine) on the compatible data files.
The primary purpose of such technology is to limit consumer choice. Microsoft predictably champions this technology in their forthcoming Windows XP operating system, as it allows them to cement relations with the powerful recording industry while leveraging their desktop monopoly to damage their (wholly superior) competitors in the media player market.
*Either: Providing a reduced set of features, but in a high quality implementation, such as Adobe's 'electronic book' readers; Or providing a wide array of features from competing products implemented in a vastly substandard fashion, such as Windows Media Player.