You can copy your "preactivated SLP" files to your unattended CD so you won't have to activate. The files are the following in your recovery media: Oembios.bin, Oembios.cat, Oembios.dat and Oembios.sig. The files may be compressed and so named: Oembios.bi_, Oembios.ca_, Oembios.da_ and Oembios.si_. Microsoft provides "template" files of these on a normal XP CD. Simply replace those with the files from your recovery media.