I don't know how comfortable you are dealing with the inner guts of your installation, so my recommendation may be all too easy for you.
There are quite some free tools that may help you finding the culprit. I would download
Sysinternal Suite, very helpful set of utilities. Use ProcessExplorer and sort by Company Name, perhaps you find something from Symantec being still active. If so, use Autoruns to identify the way this is started. If you can't find something, you may try
Unlocker. This handy toy shows you blocking handles for a specific soft- or hardware. Still in trouble? Perhaps you can fix it simply by removing your drive from the Device Manager and adding it again with a search for new hardware. After that I would skim through the registry for the rest of entries with "ghost" in their names.