To make this simple, you can look in the back of your computer where your onboard sound card is located. 5.1 capable cards will have 3 holes for speaker input (front channels, rear channels, center/sub) More often than not they will be color coded as green (front channels), black (rear channels), and orange (center/sub). Additionally there will probably be an input for a microphone. If you do not have a 5.1 capable sound card, check out newegg.com. You should be able to pick up a quality 5.1 card for around $60.