Scratch

the special part about this you don't need to go to the store and buy an actual 4 speaker set, as long as you have to sets of 2 speaker it should work, I'm pretty sure right now you have one set of speakers plugged into your "green" audio port, you should leave that there, now go find yourself a pair of speakers for your surround sound, once you found them set the speaker in position where you want and plug in the electrical cord, now plug the audio connector into the "blue" port, the blue port is just another line, it's really meant for plugging in an MP3 by using a special connector cable and playing music because it is called "line IN", however if you plug in your speakers right now and turn the second pair on nothing should happen, unless your motherboard or soundcard drivers are smarter than most, somehow you should get a pop-up saying a device or speakers are plugged in, find your way to some setup things for your motherboard and switch the blue port to "rear left and right speakers", the reason this may not work is each motherboard is different and drivers may not react correctly to the extra set of speakers being plugged in, if it does work, lucky you! you now have a much higher quality speaker set!

other notes:
-if your computer is old it might not be able to handle the use of 4 or 5 speakers
-there might be 5 or 6 speakers because some sets of 3 speakers include a small subwoofer (don't worry mine is 6 speakers and it works fine!)