Windows Server 2003: How do grant a user permission to create user accounts without adding to administrators group?

Simple newbie question I am sure. But I can't seem to find the information anywhere.

How do grant a user permission to create user accounts on the local machine without adding to administrators group?

I am working on a website that is setting up ftp user accounts, and I need to give the Network Service account the ability to create users.

I thought it might be the "Act as part of the operating system" permission in the local security settings, but it does not seem to be working for me.

Any Ideas... Thanks

As far as I know, you can't create (or manage) local users without having local administrator rights.