Pre-activation" of Windows XP by the OEMs will be done in one of two different ways depending on the OEM's own configuration options and choices. Some OEMs may protect Windows XP using a mechanism which locks the installation to OEM-specified BIOS information in the PC. This technology works very similar to existing technologies that many OEMs have used over the years with the CDs they ship to reinstall Windows on these computers. We expanded and integrated the existing OEM CD BIOS locking mechanism with product activation, and call this method of protection "System Locked Pre-installation," or SLP. Successfully implemented, SLP uses information stored in an OEM PC's BIOS to protect the installation from casual piracy. No communication by the end customer to Microsoft is required and no hardware hash is created or necessary. At boot, Windows XP compares the PC's BIOS to the SLP information. If it matches, no activation is required. Every single piece of hardware could be changed on a PC with SLP and no reactivation would be required — even the motherboard could be replaced as long as the replacement motherboard was original equipment manufactured by the OEM and retained the proper BIOS. In the unlikely scenario that the BIOS information does not match, the PC would need to be activated within 30 days by contacting the Microsoft activation center via the Internet or telephone call — just as in a retail scenario. http://www.microsoft.com/technet/prodtechn...te/xpactiv.mspx