This application should have its own uninstaller that can be accessed from the Control Panel > Uninstall a program. Access this feature and look for HCN Messenger on the list, then initiate the uninstall operation. If you encounter an issue, then I recommend you to use Revo Uninstaller. Even if it can't uninstall the application normally, it will force it to uninstall by wiping out all traces of its presence from the system.