Hoooo boy...
I've been dealing with Norton Systemworks / Antivirus / Internet Security problems for a long time, and it seems each one is different than the last. I actually quit using it on customer systems (and my own) because sometimes it was uninstallable.. And if it did install, it became un-uninstallable.. Believe it or not...
Honestly, it's not even that "good" of a virus scanner, despite the nice interface. I switched to Kaspersky Personal Edition - Tremendously better at finding and removing viruses, albiet slower.
There's a variety of issues I'm familiar with, but I think the best suggestions are on Symantec's website. They offer many suggestions (as this is a very well known problem), most of which work.. usually.
The following documentation may help you out:
http://service1.symantec.com/SUPPORT/nav.nsf/docid/2001092114452606
What I have done in the past to solve your situation is the following. Please understand that while I have done this many times without error, I have also had a couple of times this has caused additional complications (Hanging services and the inability to get online, mainly) or not worked at all. So the potential to create more problems exists and you should be prepared with a backup of important data... etc.. JUST in case. But no matter what happens, we'll be able to help you out I'm sure.
- Uninstall ALL Norton products from your system.
- Reboot your computer and enter Safe Mode (tap F8 a split second before the Windows logo appears on startup)
- Delete (if you have these folders): C:\Program Files\Symantec; C:\Program Files\NAV; C:\Program Files\Norton Antivirus; C:\Program Files\Common Files\Symantec Shared
- Use the registry editor (Start/Run/regedit.exe/OK) to delete the following keys: HKEY_CURRENT_USER\Software\Symantec; HKEY_LOCAL_MACHINE\Software\Symantec
- Reboot the computer
- Make an attempt to reinstall Norton AV/SW or IS 2005
And yes, while I've been able to resolve most Norton installation / uninstallation problems, there has been at least one that I was unable to fix.
So don't feel bad if you can't figure it out or it is too much of a headache. There's an answer out there somewhere.