The laptop may have been given a fixed IP address in the same subnet (IP address range) as the router itself, probably a 192.168.0.x address.
Open the Network Connections folder, right click the Local Area Connection and select Properties. Highlight the entry for "Internet Protocol (TCP/IP)" and click the Properties button. In the properties sheet that opens, select the two options:
- Obtain an IP address automatically
- Obtain DNS Server address automatically
The adapter will then get its addresses automatically by DHCP directly from the ISP