MAC OS X PDC questions

hi all i set up a domain at home with 10.4.8 server with the intention of learning more about windows domains for some projects at work. i use macs where possible, which is why my home domain is not controlled by a windows server. i have managed to create and log on to windows machines (a mix of XP Pro and Server 2003 installs) to the domain, but can't seem to do a lot with them. i log on to the windows machines as 'diradmin' - i assumed this would be the domain administrator account and would be able to do anything, on any machine in the domain. i have not set up any other accounts as yet. but wirh diradmin i cannot install programs, run certain apps, open administrative controls, or even access certain folders. i have gotten so far by making it up as i go along, but i may be misunderstanding a concept or ten. if anyone can tell me how to create/change an account with domain-wide administrative powers i'd be very grateful. thanks in advance