How did you disable the HDMI? Unless you have an HDMI cable connected normally the audio is not switched to the HDMI link. If you disabled it in the Device Manager that may have had some affect on the Digital Out. If this is the case, enable it in the Device Manager but make sure your "Speakers" are set as the Default Playback device in the Sound Panel. Then you may be able to reset the RealTek for digital out.
If that doesn't work, unfortunately it may take a factory reset (reinstall) to get it working the way you want.