Summary: 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.
Related:
Why did my home network stop working? Home networks or other small LAN can stop working for various reasons, but there's a simple reason home networks stop working that's often overlooked.
How should I set up my home network? Once you add a second computer, you're faced with setting up a network, at least to share the internet connection. Here are some general guidelines.
Experts Exchange - Windows System Error "duplicate name exists on the network" - includes a couple of geekier approaches should the problem persist.
Article C2801 - October 4, 2006
i am in a university campus at the moment and i am facing this problem 'a duplicate name exists on the network'. If i change the name of my computer and the workgroup how will i exchange information with the rest of the university workgroup?
Posted by: despina at February 27, 2007 10:23 AM-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Change the name of your computer, not the name of your workgroup.
Leo
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (MingW32)
iD8DBQFF5JWZCMEe9B/8oqERAsQqAJ9MpDj8qAZ9kfU/gEM1e/Zh8tNsLACdFYmH
Posted by: Leo Notenboom at February 27, 2007 12:33 PMTQKWV2EqUgZCAFWDv1Mmf1I=
=ch90
-----END PGP SIGNATURE-----
Windows system error- a duplicate name exists on the Network". This could be because of a duplicate name used in the Network connection. Every computer should have a unique name in the network, in order to be identified in the Network. To resolve the issue, I suggest you change the name of the computer by performing the following:
1. On the Desktop, right-click MyComputer.
Posted by: vishal at July 5, 2007 9:26 AM2. Choose Properties.
3. Choose the Computer Description Tab.
4. On the window displayed, click the Change button.
5. This will open another window.
6. On the displayed window, Type the new Computer Name.
7. Do not modify anything with the Workgroup box.
8. Click Apply, then O.K.
This can also happen if you have an ethernet connection, and inadvertently enable a wireless card at the same time. DHCP assigns two leases with the same name but different IP addresses. Solution is to disable the wireless, check ipconfig at the client, then delete the other lease at the server.
Posted by: Michael Layden at July 5, 2007 4:12 PMAn article at Stanford's School of Earth Sciences gives a reason why this might continue to happen.
Posted by: Cecile Dunbar at September 25, 2007 11:52 AMLink to it here
http://pangea.stanford.edu/computerinfo/resources/network/faq/windupname.html
Actually, I had the same problem this morning when I got to work. I tried all means but none work. I decided to change my IP address and domain name.. Guess, what happened.. it worked perfectly and all is back to normal.. Thanks for your thread though.
Posted by: Mac-Jordan at October 9, 2007 7:05 AMI have worked/asked/searched this problem on our network for two - three weeks.
The solution was surprising and had nothing(?) to do with this error message.
By isoliting a small part of the network, using new cables and a new switch everything was OK, and I could continue from this.
What caused the error message?; a damaged cabletip(I don't know the English name) from the 3Com AP to the switch, tightly bundled cables, old equimment or a a pupil/teacher who has put a cable into the wrong connection. I am not sure, but my bet is the cable from the AP to the switch.
I hope this could be of help for some? Let me know - - -,
Posted by: Eldmar Korsnes at February 13, 2008 1:51 PMeldmar@gmail.com
Thanks! I had this problem because I configured a NAS device to have a device name that matched the workgroup name. The message popped up on each computer on the network as soon as they started up. Changing the hostname on the NAS fixed the problem.
Posted by: Jac Goudsmit at December 25, 2008 8:47 PMThis will help you . . .
http://www.tech-archive.net/Archive/Windows/microsoft.public.windows.server.dns/2005-06/msg00224.html
Posted by: Rohit Bansod at January 14, 2009 10:00 AM