The audio device driver is substituted by some programs that install their own sound driver, so the default driver is probably not deleted. When you uninstall such a program you will remove the driver it installed, but the default driver can be reset or restored from the Control Panel \ Sound and Audio Devices. Try the following to restore the default driver:
Go to the Control Panel, Sound and Audio Devices, and on the Sound and Audio tabs, click on the drop-down window, and select Windows Default and/or Default Device.
If the Sound and Audio Devices is grayed out and settings are not available, that means the default driver was deleted or is uninstalled. You can either reinstall it manually with a relatively complicated process, or automatically with one of the following options:
Go here; http://www.intel.com/p/en_US/support/detect
and click on "Check your system for the latest updates" the scan should detect your missing driver and auto install it.
Or download one of these freeware driver utilities:http://fileforum.betanews.com/browse/Drivers/Driver-Utilities/popular?license=freeware&os=windows
This one is $29.95 but is very dependable and will detect missing, outdated or corrupt drivers and download/install them on any brand of hardware