Shoutbox

I am quite sure the problem isn't your router.  That IP address you gave for the desktop didn't fall from the sky.  It must be statically configured, which also explains why it isn't acquiring one from the router.

Go to Network Connections folder, right click the local area connection you are trying to use, choose Properties.  Select TCP/IP protocol, click the Properties button.  Set it to obtain an IP address automatically and obtain DNS servers automatically.

You may need to right click the connection again and "repair" it afterwards.