Power woofer model OG-5050

Is this your 5.1?

http://www.newegg.com/Product/Product.aspx?Item=N82E16836131001

Use a splited cable, connect C (centre speaker) and D (subwoofer) to the orange socket on your sound card.

Use the non splited cable, connect front left and right speaker from A on speaker to green socket on sound card.

Use the non splited cable, connect rear left and right speaker from B on speaker to black socket on sound card.

They are colour coded.

Read this, it will help:

http://www.hobby-hour.com/electronics/sound-card-color-code.php

Also, read the instruction manual:

http://www.dctfactory.com/menu_pdf/5050.pdf