Needing explorer to discharge NP dll

Hi all!!
My setup actually installs my mini-rdr and start services withou rebooting
Now, I need to do the same during uninstall.
Actually, it does its job but I cannot install it again before restarting.
It happens because explorer locks my NP.dll.

Is there a way to inform explorer to refresh and discharge my dll?
…or any other object it has locked up?