win2k serv does not start - help

I have installed a Sygate Firewall 5.5 on my Win2k Server and have made some
changes in smtp virtual server.
After reboot it does not start. It stops on the window called: Preparing
Network Connections...

How to return to the previous version(working) of my system? When I start my
system in Safe Mode it runs but I can not uninstall this programme and can
not do any changes in network configuration. When i try to start system in
Safe Mode with Network it stops in the same point as in normal mode. It does
not reach window with logging to the system.

How should I try to repair it - do not want to lose existing configuration
files - It is a lot of work to configure it once again.

I would be very thankfull for any help.

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