Computer Sound Broken

Hey all,
My computer's sound hasn't been working recently. I built the computer and the sound used to work when attached to speakers, but now it doesnt work with anything (speakers or headphones). I'm running a Vista 64 Professional SP2.
Any help would be much appreciated.

 

Does the Playback device show any sound being played when an speaker is attached?

Like the green bar, does it moves when music is playing?

 

try downloading the drivers for it(google your mobo model drivers if youre using onboard)

 

Go to device manager and make sure that nothing related to sound is disabled or non-functional.

 

Yeah, the volume control moves like a green bar as if music is playing.

Under device manager for sound I have
1. ATI High Definition Audio Device
2. High Definition Audio Device

I don't know where to check if those are working or not in the device manager, but in sound settings/volume control it says they are working.

 

Go to your motherboard manufacturer's website and look up the most up to date drivers for your sound card (I'm assuming you're using integrated sound) and download/install them

If that doesn't fix the problem, and you know for a fact it isn't anything with the speakers or headsets, then I'm pretty sure your sound card has failed. If all else fails, contact your motherboard manufacturer on what to do next, most likely a return assuming you're still under warranty.