They might have called the whole thing including the BIOS strings SLP back then, don't remember exactly 😀

Most if not all pre-hacked bioses you can find on those sites/boards contains the strings for XP SLP in addition to the SLIC 2.0 or 2.1 tables.

Abusing volume licences was a lot easier with XP than later Windows versions, and it worked just as good as the method I suggest back then, but I'd guess most "public" pirated VLK:s are blacklisted now. If you can get hold of a VLK from your work/school/some other organization, that hasn't been pirated, it's another story though.