Firstly, go to the Program Files (X86), then access Blustacks and look for HD-Quit.exe. Double click this item and all the background services will stop, then you can continue with the uninstall part following the below indication.
Try using 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.