Demoting a domain controller

[Nesreen]

I have 2 servers in my domain, server 1 and 2. Each is a stand alone domain controller. Everytime i try to run the dcpromo on server 1, the active directory fails to complete uninstalling. First, it asks for the username and password of my other server (server2)and when i put the ones of server1,i get this message:
The operation failed because:
Failed finding a suitable domain controller for the domain hhh.com "The specified domain either does not exist or could not be contacted"

Can anyone help me with this problem?
Does it have to do anything with a built trust or so? what should i check for?