Into the Run window, type devmgmt.msc and hit enter.
In Device Manager, expand Sound, Video and Game Controllers. Right click the Realtek device and select Uninstall - you should also get a prompt to remove the current driver, tick the box to allow this and then proceed with the uninstall.
When this has completed, restart the notebook.
When windows has reloaded, open your Downloads folder, right click on the Realtek installer and select 'Run as Administrator' to start the installation. When this has completed, restart the notebook again and let windows fully load for a few minutes before checking.