Hi! Did you recently uninstall BearShare or other programs like it? Try Uninstalling the Device and Re installing it again. Here's how:
RIGHT click "My Computer"
Properties then the "Hardware" tab
Go down and expand [+] the Sound, video and game
If there's a yellow question mark(?) in one of the devices, RIGHT click on it and then "Uninstall" You'll get it back, don't worry.
Click Start again
Add Hardware. This will find the device you just uninstalled. Click on the one you JUST deleted and then Next.
It should be re-installed now.
Go back to your Control Panel and then Sound and Audio. Play around with the speaker settings and see if that helped you....
Sometimes you need to go back to the Device Management after reinstalling,
scroll back down to the Sound card you just reinstalled, right click and then "enable" it
Alternatively, you can use System Restore to restore your computer settings to a certain day, maybe the day before you installed a certain program which deleted your sound settings...?
Best of luck!