How can I get symantec virus software to stop scanning drives when I've already uninstalled it?

Hi all,

I have virus software I can't get rid of and I'm hoping someone can help me. In college, I was required to install symantec norton for mac on my powerbook to use the network. I've since removed the software, and yet norton still attempts to scan external hard drives and flash drives for viruses. The wierd thing is that my system profiler says norton is still on start up but when I follow the file extension to delete it I can't find anything. Driving me crazzy! Any thoughts? I've already removed all traces from the applications folder and system preferences.

Thanks