It is possible.
Here is a ghetto way to do it. You won't get left and right channels but I'm sure you'll get over it.
1) Get a pair of headphones from the dollarstore
2) cut the wire half way through and strip the ends
3) strip the ends of the wires coming from the speakers
4) connect both positive connections from the speakers to one of the wires from the headphones and tape them together.
5) do the same with the negatives
*Make sure the positives and negatives aren't exposed and touching each other
6) Plug in your speakers into your sound card
As ghetto as it gets
Another way is to get an Amp/receiver and make sure you have an RCA -> Speaker cable for your soundcard.That is the best method seeing as you will be able to push more power through.