have you tried the other port?
try setting the IP and subnet mask manually, check what's the IP of the other computer and change only the last number... (i.e. xxx.xxx.xxx.a - where xxx are the numbers in the other PC and a is a unique number which you don't have on your network.)
subnet should be 255.255.255.0... but check how it is with the other computer.
to get the info from the other computer get to the console (Run->cmd)
and type ipconfig.
oh, and copy the gateway too.
try pinging the other computer and the router and see if you get anything...
if that doesn't work make sure there are no firewalls on.
try using the network cable from the other computer - maybe your cable is damaged...
and if all fails, try restart

heh, sometimes with no apperant reason, things just work if you shut down your computer for a minute and try again... i'd also suggest shutting down the router for a minute too, and starting it up before you turn the computer on.