Are you logging into the machine locally (using the keyboard that is plugged into the Win2K Server), or are you trying to connect over a network connection, like with Terminal Services?
Because it sounds like you modified a User right you should not have.
There are a few rights that if you change them, that you can lock yourself out of the machine.
"Access this computer from the network" - if you remove all groups/users from this right, then NO ONE can connect to the machine remotely. No TS logins; no mapping drives; no accessing shared resources. Normally, Everyone has this right. You can change this to Domain Users, but that is about as restrictive as I would go (unless it is a public web server).
"Deny access to this computer from the network" - any user/group you put in this right will NOT be able to connect remotely. This will OVERRIDE the other one I just mentioned. So, be careful using any DENY right.
"Log on locally" - This group tells you who can log into the machine using its own keyboard and mouse. This is the "I'm standing in front of the computer and I want to log in" user right. This should have your Domain Admins listed, and that is all.
There is also a Deny Log on Locally, that does what you would expect to do.
So, try and log on locally. If you aren't, then try and log on remotely. Hopefully, one way or the other will let you in, and you can then make the changes to put the Win2K server back to what it was.
And be careful next time!
