Recently the sound on my laptop (HP/Compaq Presario F500, 10 months old) stopped working for no apparent reason.  I hadn't installed any new hardware/software or anything else unusual which it might have been linked to and the sound has always worked without problems before. I am using Vista Home Premium (ver 6.0 build 6000) and my sound card is Conexant High Definition Audio.

 In the toolbar speaker icon there is a large red cross next to the speaker (unfortunately it is not just on mute...) and when you ATTEMPT to open volume control it shows no volume sliders and simply reads "No audio device is installed". However, when I open device manager, it claims the sound card is working properly. I thought it might be a PROBLEM with the driver so I searched online for a new driver, found ONE which seemed to be a fix for this problem [4.15.0.50 A] but it made no difference. I then used the auto-update feature in device manager to find the latest driver, which it did (I now have 4.33.1.61) but this still made no difference.  I have tried rebooting the computer with the new drivers and disabling/enabling the audio device to no effect.

I am pretty much a novice at computers so there may have been SOMETHING obvious I missed, but there seem to be a few other people out there who have had this problem, and the only fixes I have seen recommended (e.g. get  newest driver etc) haven't worked for me.

Any help would be GREATLY appreciated!
Cheers.BTW, computer has Athlon 64 X2 Dual Core TK-53, 1700mhz with 958mb of RAM. I have Norton 2007 installed (though the subscription has expired).