Before you can load the driver once again on your system, try to uninstall the old one. To do that, go to Start, right click on My Computer > Properties and go to Device Manager. A new window should be opened. Search through the list provided and click on Sound, video and game controllers then right click on Realtek High Definition Audio and select Uninstall. After the process is completed, reboot your computer. When you computer starts, if the driver is not automatically installed, try to do it manually. If the problem still persists, contact the manufacturer on the official website.