Go to device manager, locate sound, video games and controller.
Right click onto Realtek, uninstall and tick delete software.
Restart PC and check if the microsoft's audio is installed.
Now download from your manufacturers site as @Phillip Corcoran mentioned up there.
Install them.
Now realtek should be in Control panel under Hardware and sound.
If not Probably it should be in Windows patrition, usually by C (where your windows is installed).
Go to windows explorer->C:->Program Files (NOT x86)-> Realtek-> Audio-> and look for GUI application (similar to RtkNGUI) and open it, that should be your control panel.
Now to make it to start up every time you start the pc/restart if you wanna I can show it to you, if you dont wanna, you...