[ActiveDir] Reassign Runat admin account?

[Stephen G. Maczko]

I have a w2k3 server DC and an XP client.   I want to be able to change the default admin account that appears when I invoke the runat on the client to be the DC Admin rather than the local Admin account.   Searched for runat in the registry, but didn’t get a single hit.   Is this possible?   Steve