Rtkvac.sys is the driver left-over. You may need to use Link Removed.
1. Disable your Antivirus/Security software
2. Uninstall your Realtek sound driver
3. Reboot
4. Disable your Antivirus/Security software
5. Control Panel > System > Device Manasger
6. Locate your Realtek HD audio device, right-click it and completely remove it
7. Reboot
8. Download and install the right driver for your audio device, I understand it is Link Removed.
9. Reboot your pc now