Improved copy protection systems including copy once, personal computer (PC) buffer copy protection, and identifying different copy control systems are provided. A “copy once” protection system uses memory in a recording device to remember content or physical media IDs so that the same original content or media is not copied twice. A PC buffer copy protection system determines if there is a relationship between input and output buffers on a PC, or networked PCs, to determine if the content can be copied. Different copy control systems, such as DVD systems and Conditional Access (CA) TV systems, can use different copy control watermark keys or payloads to identify which type of copy control system should be implemented.