Sound card not detected?

[dosu66]

I got a new computer less than 2 months ago (Dell Inspiron 530s, running Vista), and a few weeks later I experienced a problem with sound/playing music. When trying to play mp3 files on my player (MediaMonkey and J River) the songs were unable to play. At the same time, I couldn't hear the audio on YouTube video, play streaming music via Last.fm, etc. The problem seemed to fix itself, so I considered it a fluke and left it at that.

Now the problem is happening again, exactly as before. I ran a DirectX diagnostic and under Sound it says:

"No sound card was found.  If one is expected, you should install a sound driver provided by the hardware manufacturer."

Does anyone know what's going on or what I can do to fix it? I tried browsing the Dell forums but it crashes my computer every time.

[Karnac]

Does device manager register your onboard sound? Any ! or ? in device manager?