What kind of "domain controller" are you using? Are you using an Apple Xserve or just a plain OS X (plus what type of OS X are you using) machine (plus what type of machine and RAM specs, etc.)? You could have not been more obscure with your super short problem description.
What are you applying GPOs to? Are you trying to apply this to Macs or Windows PCs?
If it's the latter, I think you might be on the wrong site. Check out some sites for Windows administration. A Google search for that should come up with a bunch of results. If you are trying to do some stuff with Macs, you might want to head over to MacWindows (http://www.macwindows.com) for some tips on using GPO with Macs (if this is even possible).