LAN doesn't show up in 'Network Connections'
Also check Control Panel -> System -> Hardware -> Device Manager
Check for your network adapter in the list of hardware. If it's not there
(which is should positively be if you are connected) run the hardware
installation wizard which will search for and install drivers.
If it is there, you may want to try uninstalling and rebooting.
This has happened to me before, re-seating the NIC card and rebooting
solved it - but as you are already connected it is obviously installed
Hope that helps
EDIT - If you want to change your IP via command line you can use netsh
with the -f <filename> parameter.
But that's slightly more complicated.