Windows Server 2003 SBS Premium Reinstall

[Rookie]

I have recently had a failed attempt at a Domain Name change and have
partially recovered Server functionality by carrying out an OS reinstall.
Current outstanding issues for which I am seeking advice/assistance are:

1. No lan/wan connectivity seems possible although system is telling me that
ethernet cards and drivers are installed and functioning correctly.

2. Am able to ping the router from the Server console but unable to ping any
workstations on the lan. Conversely the Server cannot be pinged from any of
the workstations.

3. From within Control Panel when selecting "Network Connections" I am
presented with a blank "Network Connections" window.

4. I am also unable to access backup software (Backup Exec) from which we
could attempt to execute a restore. Something to do with the Backup Exec
process not starting.

If anyone has any thoughts on how I could return full functionality to this
Server without having to carry out a complete teardown and rebuild I would be
greatful.

Regards,

Rookie