I believe your video card, 9500GT, has a 2-pin SPDIF input for digital audio. Now check if your motherboard (or audio card) has a SPDIF output. If it does, then it's an easy setup, as follow:
Try to find a 2-pin SPDIF cable, you probably have one from an old audio card or CD/DVD drive. It looks like this:
Connect one end to your 9500GT SPDIF input and the other end to your motherboard or sound card SPDIF output. Newer motherboards usually have 5-pin SPDIF, and depends on the board, find the ones that said SPDO (SPD Output, connect to the red cable) and GND (Ground), connect it to the white cable.
Now you should be able to get audio and video from the 9500GT's HDMI out.