Lost Active Directory

Help! I’ve screwed up. I was playing around with group policies on my home network (w2k Advanced sa the DC). Somehow I’ve locked myself out of everything to do with Active Directory.
It could have been “Deny access to the computer from the network”in in the default domain group policy. I chose domain users to deny access. I didn’t think it would apply to the administrator.
I cannot access Active Directory or any security policies.
How do I get my rights back?
Thanks