Click Start, right click My Network Places, Choose properties, double-click Local Area Connection and then click properties.
Highlight Internet Protocol TCP/IP and then click properties. This will open you IP settings. Here, you will see what IP address is configured if any. Or if "Obtain IP address Automatically" is checked.
If your router is setup to hand out the IP addresses to requesting machines then you definitely want to have it set to automatic. If your not sure, I would just write down what is currently in the settings, reset it to obtain automatically and reboot. It really can't hurt, and my gut feeling is, it will fix it.