|or use the stereo for watching movies.|
Stereo relates only to audio, it has nothing to do with video.
The only difference between a crossover cable and a standard patch cable is the way the plugs are wired at one end. Does the stereo have an Ethernet socket or a USB socket. If it is USB it is unlikely to accommodate a USB the Ethernet connection.
If it is Ethernet you will need a crossover cable if you are plugging in directly to a PC netwrok card.
A model number of the device you are trying to connect to the PC would help.