Basic netsh command to reset the tcp/ip...
Open the command
Enter netsh winsock reset
Restart your computer.
How to reset Internet Protocol (TCP/IP) in Windows XP
In some case, uninstalling TCP/IP and reinstalling will do the same fix.
A nifty and easy to use GUI software that easily does the repair and reset for users is this>
Okay the ZA database is easily done....
Boot your computer into the Safe Mode
Navigate to the c:\windows\internet logs folder
Delete the backup.rdb and iamdb.rdb files in the folder
Clean the Recycle Bin
Reboot into the normal mode
The Zone Alarm will be cleaned of all previous settings and data and it will appear as when it was first installed
After the reboot into normal boot, the DNS and DHCP servers will have to be re-entered and as trusted.And do a new setup, if the previous settings have not be backed up.
Something off the topic, but of some interest...
How to troubleshoot TCP/IP connectivity with Windows XP
Since you have a lot more experience in the PC world than I do, the MS Knowledgebases may be of some interest to you, since they are the genuine thing.