LAN trouble--Red X

I'm trying to install camera software on a friend's XP. Actually, the
camera is outside the house, and there's an intermediate box connected
to the PC by an ethernet cable (crossover). The camera is plugged into
the box. I'm pretty confident that we have the right TCP/IP addresses.

If I got to Control Panel, I see two network icons: LAN and
RealTek8139. He doesn't really have a LAN. I'm guessing the realtek port
is the the ethernet port on the PC.

With everything in place, one fires up the camera software, and presses
the Connect button. It should turn green, but does nothing. No green
button and no picture. Comments?

Here are the instructions from the Sentinel (camera) arrangement for
setting IP addresses.
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The Video Sentinel box contains a micro-controller (RCM3200 from Rabbit
Semiconductor) with an Ethernet port that has been configured with a
fixed IP address. By default, the IP address of the Video Sentinel box
is 10.0.0.50. This address is set in the firmware of the
micro-controller and should allow the Video Sentinel box to be used
in a local network. If a different IP address is required, however, the
firmware can be changed at Sandia.

The Network Interface Card that you use to communicate with Video
Sentinel box should be set with a compatible IP address. For example, I
typically set the IP address of the NIC to 10.0.0.2 and set the Subnet
Mask to 255.0.0.0.