i had the same problem. usually the ip addresses of a computer in a small network should be 192.168.0.x where x is any number. if the computer connect to internet through another computer, then the default gateway should be 192.168.0.1 otherwise it will not have a default gateway. try this:
go to a command line.
enter "ipconfig" or "ipconfig /all" without the quotes
you should see ip address, and subnet mask. subnet mask usually is 255.255.255.0 and ip address 192.168.0.x (x is any number).
next try ping
in command line type "ping 192.168.0.x" and see if the pc can find itself on the lan.
if it can find itself, next try "ping computername"
if it can find itself by computer name, it's a good sign.
next go to control panel, admin tools, services.
check to see if "TCP/IP NetBios Helper" is enabled and started. if it's not started, double click on that line in the general tab, choose from drop down box of "path to executables" automatic. the path to excutables should like:
C:\WINDOWS\System32\svchost.exe -k or something similar.
after you enable it to automatic, go to dependencies tab.
there should be "AFD Network Services" and
NetBios over TCP/IP with a plus sign, click plus sign.
under it, there should be "TCP/IP Protocol Driver" with a plus sign, and under it there should be "IPSEC Driver". if you can find these, post a reply to see next.
next you can assign a static ip address to the pc. just like 192.168.0.x and 255.255.255.0 for subnet mask. you just have find out which computer in the lan is not using x.