System Locked Preinstallation
http://en.wikipedia.org/wiki/System_Locked_Preinstallation
http://technet.microsoft.com/en-us/library/bb457078.aspx
Microsoft Supplied Keys for Preserving OEM Pre-Activation when Re-installing Windows XP:
| Windows XP Professional (32-bit) | MVF4D-W774K-MC4VM-QY6XY-R38TB |
| Windows XP Professional (64-bit) | FM634-HJ3QK-6QVTY-RJY4R-XCR9J |
| Windows XP Tablet PC Edition | XT67V-GY7FW-GR6FR-WDK2C-8T97J |
These are official keys to be used for SLP systems when activation is required.