What happens

When this error message appears it means that the server you are trying to connect to will not accept your request to connect because it does not recognize you. Logging on to a server requires your user name and password to be validated and if this does not happen, no connection can be established. Another reason for this message to appear is when your computer tries to send an unneeded password or user ID to a server where a connection already exists.

Three things you can do when The user name and password are not ...

The problem may not lie with your computer. The server you are trying to connect to may be having technical problems, in which case you should wait a while to try again to see if the connection can be established. If not, the problem could be with corruption of the data in the server which has changed your log in details. In this case, you should contact the server /network administrator and ask for your user name and password to be reset so you can register again.
Of course the problem may be simply that you are typing in the wrong password and user ID. Check to see if what you are using is correct and if you are using a password manager, check to see that the information is correct or if it has been corrupted for any reason. If the log in details you are using are correct and you do not want to wait for the administrator to respond, you could try accessing the server from a new computer account. To do this click on Start, type User Accounts and on the control panel that opens, click on Manage Another Account and then on Create A New Account. Enter the details required and click Apply /Finish. Reboot your computer and then try accessing the server again. If you still cannot log on, the problem almost certainly is with the server and you will need to press the administrator to correct the problem.
In case the message appears when a broadband connection has been established simply open your browser, click on Tools > Internet Options > Connections and then select Never Dial A Connection. This will prevent attempts to create a dial up connection when a broadband connection is operational.

TipFor more information, please see: How to fix Connection error #815