Microsoft Knowledge Base Article 899356 contains the following summary:
Microsoft has released a white paper that explains how to preserve the preactivated status of Microsoft Windows XP when you use one of the following methods to reinstall Windows XP:
|•||You use the sysprep –reseal –mini command.|
|•||You modify the OOBEinfo.ini file.|
|•||You perform a manual install.|
|•||You perform an unattended install.|
Note Original equipment manufacturers (OEMs) frequently preactivate Windows XP software that they install on the computers that they manufacture.