Admin user account locked out - need help!

I was playing with the local security policies in my computer and I accidentally added the admin account to the deny log on locally user right. This computer is networked to a windows server 2003 pc. I was just trying to over ride the local security policy by placing the windows xp computer account in the OU and then linking it with the GPO with a domain security policy but it was giving me adminitrative account for the log on locally user right. So after moving the computer account to the OU, I lost all the secure connection between the client and the server. Now the problem is that I dont have admin rights to rejoin the pc to the domain again. So can anyone tell me how to recover the admin rights on this machine?

You can try to use the Resource Kit tool NTRights to remove the administrative from the user right for deny logon locally. This Resource Kit Tools for Microsoft Windows Server 2003 are a set of tools to help administrators streamline management tasks such as troubleshooting operating system issues, managing Active Directory, configuring networking and security features, and automating application deployment. Download it from here.

You can also try to set Logon User Rights with the Ntrights.exe Utility. Ntrights.exe is a Resource Kit utility that can be used to set user rights from a command prompt. Ntrights.exe can be used to manipulate the rights on either the local computer or a remote computer. The Help output for Ntrights.exe does not list all the logon rights that can be modified. More information can be found here - http://support.microsoft.com/?id=279664

If by any chance the above solutions dont work in your case then you can try to copy the security file from the \windows\repair folder to the \windows\system32\config folder after renaming the same security file in that folder. But note that this method could not be performed when the operating system is running in normal mode, you will have to do it by using the Recovery console method, check how to do that on this link - http://support.microsoft.com/kb/314058