Changing adminstrator profile

I recently joined a company and all computers login to XP Pro as administrator, the problem I have is people load all sorts of software and I want to stop that. I added other administrator accounts with the intension to change the original admin accounts to restricted users but as soon as I did that, the original admin account was lost, I could only login remotely or in safe mode. How can I add new users or is there a new way to handle this?? All these computers are on the network.