This is one of the reasons to use DHCP. You can change settings like this in bulk by modifying the options on DHCP ranges. If static addresses are required on your clients, you can use reservations and still make modifications like default gateway as needed.
The <a href=”http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/netsh.mspx?mfr=true”>Netsh utility</a> could help with that task, using the <a href=”http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/netsh_int_ip.mspx?mfr=true”>Interface IP context</a>.
You could also use Powershell. That is what I have done in the past. Here is a link that may help.