Helping people with computers... one answer at a time.
A duplicate name existing on the network happens when two resources - usually computers - have been given the same name. We'll look at how to check, and where to fix it.
Windows System Error: A duplicate name exists on the network. I get this message in a little nag box when I sign on. It doesn't come up every time, so has someone hacked in to my computer?
It's unlikely that you've been hacked.
It's more likely that the error message is exactly right: A duplicate name exists on the network. The question you're probably asking is, "what name?".
Your computer's name.
Right click on My Computer and click on Properties. Then click on the Computer Name tab and you'll see something like this:
Yours will of course have different computer descriptions, names and Workgroup names.
The error message is complaining about the Full computer name listed there. Each computer on your network must have a unique name. If two computers have the same name "a duplicate name exists". In such a case, some network operations may fail because there's no way to tell which computer you mean when you specify the computer name.
Computer names should also be different than the Workgroup name.
Pick one of the two computers that have the same name, and pick a new name.
To change the name, on that Computer Name dialog, just hit the Change button, and you'll see a dialog such as this:
As you can see, you can change your computer name to whatever you like, or change the Workgroup it's a part of. (You probably want all the computers on your network to be a part of the same Workgroup to enable file sharing more easily.) Once you change the computer name, OK your way back out. Reboot and see if the error message you were seeing hasn't disappeared.