I have a pc on our company network that I am having trouble logging on with. When you first turn the computer on it comes to the windows XP login screen. On the attempt to login you receive a windows system error message block. The block has a red circle with an x in it and the message "A duplicate name exists on the network". This is of course not the case as all of our associates have individual and exclusive names. You get this no matter who's login name you try from this computer. After you get this message you have to reboot the machine to attempt to get on again. If I unplug the network cable I can log into the computer and plug the cable back up and all network functions seem to work, except the associate does not show up on the network computer list.

This computer is a Dell Dimension 1100 with a Celeron D processor.

Any help on this would be greatly appreciated.

I've had similar (although not identical) problems caused by renaming an account. The original account name stays in XP (check the profiles in Documents and Settings) - yet the change is reflected all over the local computer.

When trying to access a workgroup the same problem occurs. Creating a new account from scratch (and deleting the old one to prevent re-using it) fixes the problem.

This is more likely to be refering to the Computer name itself. Each will have to have a unique name on the network. Try changingthe name of the laptop. This should resolve the issue. This normally happens when doing a Ghost build of a machine and not removing the Computer network details using sysprep.
I hope this helps.