Thank you for the quick response.
I only saw a single entry of hammerfall DSP in program list(program and features from control panel), but I un-installed it anyway. Of course, this removed both HSDP setting and the mixer. I restart the system, re-installed the latest version of the driver again.
Now I only got one HDSP setting, but saw two instances of the mixer instead of HDSP setting. Only one of them seemed to be connected to the actual card. I closed the one that is not working and restart the system. So far it seemed neither of the problems is appearing for now.
Only problem still left is though, I still see orphaned entries listed for hdsp32 and hdspmix with the missing icons when I go to customize notification area. The Legit ones says 'Hammerfall DSP setting' and 'Hammerfall DSP mixer' respectively with a proper icon for each.
Any idea?