.Kext error message

Several months ago I loaded HP software for a scanner on my mac. I decided not to use the scanner and deleted the software. I continue to receive this error message:
The system extension"System/Library/Extensions/hpplugininit.kext was installed improperly and cannot be used. etc
I no longer have this installed, I have trashed it and I continue to get this "phantom" message.

How can I get rid of this? Please help.

Thanks