No sound comes out of computer after I purchased a new video card?

My 3 year old computer recently died, so for christmas my parents bought me a custom built new computer. I did however keep my monitor. The new computer's video card is the Nvidia 9600 gt, and it works great, but now no sound comes out of my Viewsonic VX2835WM monitor? The sound before worked perfectly fine. We tried everything but nothing seems to work. I have a Realtek HD audio output. Any help would be GREATLY APPRECIATED:)|||Did you reconnect the monitors audio cable to the new computer? Is it in the right connector?|||I would trouble shoot with buying a Sound Blaster Audigy SE card $30.00 from Tigerdirect.com and plug your Viewsonic into the green port. If no sound you need new speakers and spend another $50- and up ; for a set of good speekers. Dont forget the heaset $16.00 Sony MDR-G45.