I didn't say this quite right.
Sorry, I'm quite sure this brings trouble.
I know it's hard but the best, and secure, would be format and install everything again.
I know it hurts... I have to do it in the past :'(
But first, I suggest:
1. Try to find the uninstaller at Symantec webpage for NAV 2004. Run and boot.
2. If you do not have any other Symantec product, try to delete the related folders. Maybe C:\Program files\Common files\Symantec shared; C:\Program files\Symantec; etc. (see under Windows and Windows\System32 if there is a related folder there.
3. Run a registry cleaner tool (see
here).
4. Clean the Symantec drivers at the following Registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\VirtualDeviceDrivers\\VDD
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Control\VirtualDeviceDrivers\\VDD
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\VirtualDeviceDrivers\\VDD