Output copy protection of protected digital content is provided by adding detectable digital information (watermark) to the protected digital content wherein the detectable digital information is substantially undetectable when the protected digital audio content is processed on a personal computer. Also provided is a device driver configured on a personal computer which interfaces with components on the personal computer that allows content to exit the computer wherein the device driver (i) analyzes the digital content for the presence of the added detectable digital information and (ii) allows only authorized exiting of the protected digital audio content. Output copy protection is provided to digital content that is derived from any source such as a CD, a DVD, the Internet, an MP3 file, a flashcard or a broadcast transmission.