How to turn on automatic logon in Windows

Use Registry Editor to turn on automatic logon

Important This
section, method, or task contains steps that tell you how to modify the
registry. However, serious problems might occur if you modify the registry
incorrectly. Therefore, make sure that you follow these steps carefully. For
added protection, back up the registry before you modify it. Then, you can
restore the registry if a problem occurs. For more information about how to back
up and restore the registry, click the following article number to view the
article in the Microsoft Knowledge Base:

To use Registry Editor (Regedt32.exe) to turn on automatic logon, follow these
steps:

1. Click Start,
   and then click Run.
2. In the Open box,
   type Regedt32.exe, and then press ENTER.
3. Locate the
   following subkey in the registry:
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows
   NT\CurrentVersion\Winlogon
4. Double-click
   the DefaultUserName entry,
   type your user name, and then click OK.
5. Double-click
   the DefaultPassword entry,
   type your password, and then clickOK.NOTE:
   If the DefaultPassword value
   does not exist, it must be added. To add the value, follow these steps:
   
   
   
   1. On the Edit menu,
      click New,
      and then point to String
      Value.
   2. Type DefaultPassword,
      and then press ENTER.
   3. Double-click DefaultPassword.
   4. In the Edit
      String dialog, type your
      password and then click OK.

   NOTE: If no DefaultPassword
   string is specified, Windows automatically changes the value of the AutoAdminLogon key
   from 1 (true) to 0 (false), disabling the AutoAdminLogon feature.
   
   
   

6. On the Edit menu,
   click New,
   and then point to String
   Value.
7. Type AutoAdminLogon,
   and then press ENTER.
8. Double-click AutoAdminLogon.
9. In the Edit
   String dialog box, type 1 and
   then click OK.
10. Quit
    Registry Editor.
11. Click Start,
    click Shutdown,
    and then type a reason in the Comment text
    box.
12. Click OK to
    turn off your computer.
13. Restart your
    computer. You can now log on automatically.

Source : http://support.microsoft.com/kb/324737