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O'Reilly Book Excerpts: Windows XP Hacks, 2nd Edition

Hacking Windows XP

Control User Logins by Hacking the Registry

Make better use of the XP login screen.

If your system contains more than one user account, or if you've set up XP to require logins, you'll have to log in to XP before you can begin to use it. But you needn't stay with the default XP login rules; you can use a single Registry key to customize how you log in. For example, you can display custom text before login, and you can remind anyone with an account on the PC to change their password a certain number of days prior to the password's expiration.

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To control logon options, run the Registry Editor [Hack #83] and go to the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion Winlogon subkey, which contains a variety of logon settings (as well as some settings not having to do directly with logons). Following are the most important values you can edit to customize logons.

DontDisplayLastUserName: This setting lets you control how the system logon dialog box is used. If this String value is present and set to 1, all users will have to enter both their username and password to log on. If the value is 0, the name of the last user to log on will be displayed in the system logon dialog box.
DefaultUserName: This String value contains the name of the last user who logged on. It will be displayed only if the DontDisplayLastUserName value is not present or is set to 0.
LegalNoticeCaption: This String value, used in concert with the LegalNoticeText value, displays a dialog box prior to logon that contains any text you want to display. (The text doesn't have to be a legal notice, but this value is often used for that purpose.) The box has a title and text. The LegalNoticeCaption value will be the dialog box's title.
LegalNoticeText: This String value, used in concert with LegalNoticeCaption, contains the text that you want to be displayed inside a dialog box displayed prior to logon.
PasswordExpiryWarning: This DWORD value lets you display a warning message to users a certain number of days before their passwords are set to expire. It lets you determine how many days ahead of time the warning should be issued. To edit the value, click the decimal button and enter the number of days.
ShutdownWithoutLogon: This String value enables or disables a button on the XP logon dialog box that lets the system shut down. A value of 1 enables the button (so that it is shown); a value of 0 disables the button (so that it is not shown).
Shell: This String value really doesn't have to do with logons, but it's one you should know about. It determines the shell—the user interface—that will be used by XP. The default is Explorer.exe, but it can be another shell as well—for example, the Program Manager from older Windows versions. Type in the name of the program; for example, Progman.exe for the Program Manager, or Taskman.exe for the Task Manager.
AutoRestartShell: This DWORD value doesn't have to do with logons either, but it's another good one to know. It sets whether to automatically restart the Windows shell if the shell crashes. A value of 1 automatically restarts the shell. A value of 0 tells XP not to restart the shell, forcing you to log off and then back on again to restart it.