Need to be an Administrator to perform this function

[vanillawafer]

Here's the scenario. I have One server in house that's still running NT 4.0. All of the workstations are mostly running windows 2000 professional. For some reason, me the Administrator can't do anything. I can't load any programs to any of the workstations, I can't change any interet settings on the workstations, I can't view settings, I can't do anything. I keep getting the error message equivalent to "you're not an admin," so you can't do this. I have no idea what the problem is. I have logged into the machine as an administrator, as well as log directly to the network as an administrator. I can't do anything. Now for some strange reason all of the network settings to get to the internet have changed. No one can get to the internet, it's a mess. What could the problem be?

HELP

 

[vanillawafer]

Let me add, I have tried re-taking ownership of the whole C drive, still doesn't work.