When Windows NT, 2000, XP and 2003 systems establish connections between each other for file and printer sharing, permissions for those connections are verified by passing a username and password from the client to the server. Many times an attempt to connect from one machine to another is frustrated by an error that reads: The credentials supplied conflict with an existing set of credentials.

When this happens, the logged-in user on the client computer usually does not have a matching account on the server. When the user tries to establish a connection normally (through Explorer), the connection is rejected. He may then try to map the connection to a drive letter by using the Map Network Drive Wizard and supplying different user credentials (the wizard allows this), but on doing so the aforementioned error occurs.

The reason for this: Windows is programmed to reject multiple connections from the same NetBIOS source if more than one set of credentials is supplied from that source. In the above example, attempting to map a drive creates two separate connections: one to determine the presence of the NetBIOS share in the first place (which passes the existing, logged-in user credentials), and another to actually make the connection (which passes the separately-supplied username and password). Microsoft claims this is by design to prevent security problems.

Another common scenario for this problem is when a user attempts to map a drive connection on another computer by using the Map Network Drive or NET USE command, and runs into the same problem.

There are two solutions. The first is to establish proper credentials on either the server or the client -- i.e., create accounts with usernames and passwords that match on both ends. This is the best long-term solution, although there may be cases where it isn't practical -- for example, lack of access to the server.

The second solution is to use the NET USE command to map the connection by using the IP address of the remote machine rather than its NetBIOS name. For example:

NET USE <drivename> \\xx.xx.xx.xx\share <password>
/user:<remote_machine>\<username>

where <drivename> is the drive letter to be mapped, \\xx.xx.xx.xx\share is the IP address and share name, <password> the password for the alternate credentials, and <remote_machine> and <username> the name of the remote machine and the user account on that machine to log in as.

Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter. Check out his Windows 2000 blog for his latest advice and musings on the world of Windows network administrators – please share your thoughts as well!