There are still plenty of these machines around so, if you find no network connection after a reboot, check that the IPSEC port is excluded from use to avoid a glare condition like this:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\ReservedPorts

Add an entry in the format xxxx-yyyy for the port range. For a single port like this, both sides are the same.  So, for IPSEC which uses port 4500, add

4500-4500

For reference, these are other ports that can be added if necessary:

1433-1434 [MSSQL](more if you have other SQL instances on the system)
1745-1745 [ISA Server 2000 or ISA Server 2004]
1080-1080 [SOCKS]
1718-1720 [H.323 Gatekeeper (ISA 2000 only)]
3343-3343 (already in many systems)
1645-1646 [IAS](Radius)
1701-1701 [L2TP]
1812-1813 [IAS](Radius)
2883-2883 [AUTD]
4500-4500 [IPSEC]
1801-1801 [MSMQ](already in some systems)
4070-4071 (BES)
3500-3619 [ISA Server 2000 only]