Unable to hear sound from Videos

I have posted this already in another thread in geek police.net but some how i wanted to ask u if u could help! Pl help....

Hi,

I was trying to watch a youtube video on a cookery website but im unable to hear sounds/audio. Sad I tried to double click on the volume symbol in the right side of the desktop, but it threw up pop up saying

there are no active mixer devices available. to install mixer devices go to control panel click printers and other hardware and then click add hardware.

This program will now close

I tried to launch the volume control from start>Program> ...etc. the same pop up came up. But i can hear general sounds from the laptop like those warning sounds. Earlier i could her that page refresh sounds. hmmm But cant hear it now. Also, i tried talking in google talk. But no luck. I cant hear a thing my mum spoke nor did she. Probably the speaker and microphone both are not working.
Pl help me.
Priya

Microphones tend not to last long, if it's hardware failure or incorrect drivers, then malware removal isn't the right forum.
Moving to hardware.

In device manager remove your mixer device if it is their with an exclamation mark. Reboot and it should detect it but not be able to install the driver. If so and in control panel install new hardware, e.g. mixing device driver using windows update.