Disable Windows XP Activation

You need to be logged with an Administrator account to perform the following operations:

• Open 'regedit' (Start > Run > Type 'regedit')
  Go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\WPAEvents
• Edit the entry OOBETimer by double-clicking it and replacing its contents withFF D5 71 D6 8B 6A 8D 6F D5 33 93 FD. 
• Right-click on WPAEvents folder and choose Permissions.
  Select System account and 'check all' of Deny Listbox. 
• Restart computer.
• To verify if Windows is activated run the following command:
  %systemroot%\system32\oobe\msoobe.exe /a
  Application shows Windows is already activated.