If you are stuck with the IP conflict issues on your network, you can try using this feature of Windows DHCP. If you plan and manage your network properly this might not be needed. It is not recommended unless there is no choice as it puts the load on DHCP server and also increases the delay in IP address issuing process.
To enable this, Open DHCP Management console, Right click on the server and click properties (In Windows Server 2003), click on Advanced tab and enter a value in Conflict Detection attempts options. By default it is 0, it is recommended to not have it more than 2.
http://technet.microsoft.com/en-us/library/cc737924(WS.10).aspx
In Windows 2008 R2, you need to expand DHCP server and the right click on IPV4 to get to this option.
