stick a laptop to a LAN

[Steven Meyer <meysteven () gmail com>]

Hi everyone,
We already had a few discussions about preventing laptop to connect to
our secured network.
My question would be the exact opposite: we have a secured network
with one laptop for external presentations.The only way to to put
anything on the laptop is threw the network (CD ROM, usb, diskette
etc. are disabled). But the real problem is how to protect the laptop
from being connected to a other network and be infected with spyware,
virus etc... and even worse having some of our data going threw other
LANs.
how could I be sure that the laptop will ONLY be able to connect to
our LAN and not any other.
Thanks for any help or hints.
Steven Meyer