This copy of Windows must be activated with Microsoft before you logon.....

After a long time using Windows XP, suddenly appeared a problem.When the computer is turned on, the computer screen displays a message "This copy of Windows must be activated with Microsoft before you logon. Do you Want To activate Windows now?".The message provides 2 options, "Yes" and "No.".If the click the option "No", then the computer will return to the login menu.And when the click the "Yes", it will display the menu activation of Windows XP, which of course require a product key to be able to do the activation.


After searching on Google and tried every trick that is given, then I found a link that shows how activation without using a product key.Sunil Jain from Tech18 provides tips and tricks as follows:
Because the Windows XP logon failure, then this trick is run in Safe Mode.

• Click Start -- > Run  

• Type regedit

 

• In the registry editor click “HKEY_LOCAL_MACHINE” -->  “SOFTWARE” --> “Microsoft” --> “Windows NT” --> “CurrentVersion” --> “WPAEvents”

 

• On the right panel, find “OOBETimer” then double click it.Now, Delete all the Values by highlighting it, then delete it.Type in this value without the quotation mark “FF D5 71 D6 8B 6A 8D 6F D5 33 93 FD”.

 

•  On the left panel right click WPAEvents, then click on permissions.

 

• Then click System or SYSTEM, then Deny Full Control, then Click OK.

• Then Exit Registry Editor.Go to "Start" --> "All Programs" --> “Activate windows”.Now the windows have been successfully activated. 

  
It seems that the problem has been resolved.Apparently not, within a few days later, windows xp again displays the same message every restart.Although already successfully activated, Windows XP still ask for activation.
From the Microsoft forum I get an answer.

If the computer can be started to a safe mode command prompt, run this to re-arm XP activation:
rundll32.exe syssetup,SetupOobeBnk
[Edit:  command must be typed exacly as above with space, caps, and comma.]