Windows XP activation

open Registry Editor (Start->Run then enter regedit and push OK button)
open the registry key at the location HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionWPAEvents
edit the OOBETimer key value and set its value to "ff d5 71 d6 8b 6a 8d 6f d5 33 93 fd"
right-click on the same key WPAEvents and select "Permissions"
select SYSTEM group/user and check all DENY options (we won't allow XP to mess with us anymore, in fact we deny it firmly :o)
click Advanced button then uncheck "Inherit from parent the permission...", press OK, when prompted at next step just answer with "Copy"
in "Permission entries" select the SYSTEM then choose "Edit..."; check all the "Deny" permissions the OK+Apply
It should not ask you anymore for software activation. In fact you could run Start->All Programs -> Activate Windows and you should get an response message like "Windows is already activated". If not working then just try again, maybe you have missed something on the way.


Source: mynixworld