• Windows authentication locks the computer from outside access.man thinking about internet security image by patrimonio designs from Fotolia.com
  
  All Windows operating systems allow authentication for security purposes. This means that a username and password is the most common form of authentication available. For authentication to work, there must be a database that holds the information to verify the presented credentials. The computer or network administrator creates the database. However, there may be issues with authentication that arise due to quirks or instabilities in the system.
  
  

Login Problems/Windows XP

• A computer login allows users to access the resources of a computer.login image by Edvin selimovic from Fotolia.com
  
  When Windows XP users attempt to connect, the login dialog box is grayed out with the username set to "Guest." However, you cannot change the username, and no password works. Furthermore, only files owned by the guest account are accessible.
  
  There are two possible solutions. If there are multiple logins for that user, remove or log out other occurrences. Alternatively, turn off simple file sharing. This occurs in the Windows XP Home edition. Open Windows Explorer, go to "Tools">"Folder Options">"View" and uncheck "Use Simple File Sharing." If necessary, disable the "Guest" account.
  
  

Double Hop Issue/Windows IIS

• IIS is a Windows web server that controls web services to the Internet.pagina web image by Bernardo Varela from Fotolia.com
  
  Sometimes users who work with IIS, a Microsoft web server, have problems logging onto an application that authenticates to IIS. In this case, their authentication occurs first at the IIS level, and when the attempt is made to connect to the application, a "double hop" occurs, and a failure to authenticate results.
  
  A solution is available by using either an anonymous access or with impersonation turned off. In either case, IIS takes care of authenticating and then it uses a different user, called anonymous, for local or network access. This avoids the double hop issue. Anonymous access allows anyone to access the site, but in this case the authentication already occurred with the user name, so security is not violated.
  
  

User Name/Password Problems/SQL Server Windows Authentication

• Integrated Windows authentication allows users to log in only once.Security and antivirus vector icons image by Aleksandr Lukin from Fotolia.com
  
  A different authentication issue occurs when connecting to a database engine, such as SQL Server 2005, on a remote server. You are not able to change the username or password under the "Windows Authentication" setting. You are able to switch between SQL authentication and Windows authentication, but when using "Windows Authentication," you run into the problem where the "Username" and "Password" text boxes are disabled.
  
  To solve the problem, go to "Start">"Run"> and run the following executable from the command line: "rundll32.exe keymgr.dll, KRShowKeyMgr." The Windows Credentials Logon Store opens. This allows you to specify different Windows authentication credentials when connecting to different servers. Click "Add" and type in the name of the remote server to connect to along with the credential of the remote domain to use when logging in to that server. Log in to the remote server and connect to the SQL Server engine by typing in the server name and selecting "Windows Authentication."