Active Directory Powershell Blog : Use Active Directory Powershell to manage Windows 2003/2008 DCs
Now HERE WE GO!!! This is how you can make the Active Directory commandlets work for Windows 2003 directories. You have to install this web service and then the commandlets will work in PowerShell for older Domains.
Active Directory Powershell Blog : Use Active Directory Powershell to manage Windows 2003/2008 DCs