some cards provide facility to transfer sound thru vga port so that you can use a converter and connect via HDMI.. i am not sure of this cos i haven't tried it... but they have port to connect SPDIF cable...
HDMI is capable of carrying both audio and video signals from the video card to the LCD monitor. The following conditions apply.
1. It must be connected to the HDMI port in both video card and LCD monitor (or HDTV).
2. If using an AMD Radeon HD video card, the sound driver for the video card must be installed.
3. nVidia video cards have no sound driver because they does not have audio processing units built in. A pass-thru cable must be connected from your sound card or onboard audio to the nVidia card for the sound to be transmitted thru HDMI.
4. Using a VGA or DVI to HDMI adaptor will not transmit the audio because VGA and DVI only transmit video signals.
5. If the LCD does not have a HDMI port, then it cannot recieve the audio signal from the HDMI cable.
6. The LCD monitor must have internal speakers or speakers attached to the monitor to hear audio.