Can't deploy SEP to client

I have just been landed with managing a working SEPM system on a number of clients.  I can't deploy SEP onto a new client.  It asks me for a "local administrator account" then gives me a dialog with spaces for a user, password and domain.  How can a local account have a domain?  I can't get it to work using any of the normal domain accounts.  Is this some special SEPM thing?  How do I find the account and password?