Duplicate IP adresses

If your windows computer complains that two or multiple computers in the same network has same IP address you can use ipconfig to release and renew the address.

Open your CMD window

Release your current IP
ipconfig /release
Get new IP
ipconfig /renew

You can also set the IP manually from network options: Control Panel\Network and Internet\Network Connections 
(if you have problems in local area network for example during lan party or something.)
Select Local Area Connection or Wireless depending which one you want to set up. Then in most cases select Ipv4 and change to "use the following IP" You can look your router settings from CMD window with

ipconfig /all

This shows information about your network.