An integrated data communication card installed in an ISA bus slot of a multimedia personal computer capable of performing communication and overlay functions and of reducing load for the computer. Such an integrated data communication card comprises a network connector connected to a network terminal for enabling transmission of data to and from a communication network; a system connector connected to a central processing unit of the computer for enabling data transmission to and from the computer; a data processor communicable with a storage device and the network connector, for processing data in an asynchronous transfer mode received from or transmitted to the network in response to a system control signal or a first control signal; a decoder for decoding the data determined not to be processed through the network in response to the system control signal, and for decoding data determined to represent compressed motion picture data in response to a second control signal; an overlay processor for generating image overlays from the decoded data for display on a video monitor; and a transmission controller for generating the first and second control signals under control of the system control signal.