This function tested with Domain Controller 2008 and Windows 7 Client.

To create do the following:

1- Open Group Policy Management console.



2- Right click on Default Domain Policy and click Edit. (That is just test, if you use practice, please create new GPO)



3- Go to Computer Configuration\Preferences\Windows Settings\Registry.



4- Now create 2 new Registry Item. Right click on Registry, click New and click Registry Item.



5- For message header, use:

Hive: HKEY_LOCAL_MACHINE
Key Path: SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
Value name: legalnoticecaption
Value type: REG_SZ
Value data: Your Message Header (For example: Welcome to Contoso Network)

Click OK.



6- For your message Text, use:

Hive: HKEY_LOCAL_MACHINE
Key Path: SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
Value name: legalnoticetext
Value type: REG_SZ
Value data: Your Message Text (For example: This is Test Message)

Click OK.



7- Close GPO Edit and GPMC.

8- Open CMD and run GPUPDATE /FORCE command.



9- Restart your Windows 7 Client.

10- Press Ctrl + Alt + Delete to logon.

11- Now, User can see your Message, before logon:




Here is Message on Windows XP client.