Hello Duke, I remember you asked this question in the old forum (Netscape 4.79 Registry Update
No, it simply saves your settings. However for some unknown reason, it might take quite a while to complete it sometimes.
Here are a couple of Netscape KB Articles explaining the "Updating Client Registry" :
What does "Updating Client Registry" mean
What does the message "Updating Netscape Registry" mean and what triggers its occurrence?
In ZoneAlarm, you can have it report all connections right?
When you finish Netscape, you close it. and somehow the update registry has been trigered.... then you check the Zone Alarm to see if there are any suspecious internet connection. If you are really desperate about it.
Please note, if you are connect through Network, it might be harder to get measure this, because there are lots of packets sending through (within your network) while you are not surfing the net.