Finally gave up and after various trials and other corruptions licked the index finger and 'Nuked' the C: drive back to factory settings.
Installed all relevant windows updates using the windows firewall and had no problems shutting down. Installed Norton Firewall 2002 and lo and behold I was back to the five minute shut down!!
Have now downloaded the latest Zone Alarm and reinstalled Onspeed and can't believe what I've been missing!
Byebye Norton!
