While Microsoft is providing a patch for all currently supported operating systems to integrate the new rules for daylight savings in New Zealand this patch isn’t available for Windows 2000 customers since Windows 2000 is not supported any more by Microsoft.
Fortunately Microsoft is has a smart tool TZEdit.exe made available that allows the manual change of the relevant registry values with an easy user interface. This is probably not the right solution for business customers but large enterprises should already have migrated their information technology to a more recent operating system.
Get the tool by searching for Knowledge Base article 914387 on Microsoft’s website where the link to the TZEdit application is near the bottom of the document. After extracting the file you are presented with the dialog shown below when running the TZEdit.exe where you can amend the Start Day and Last Day settings as required.