I just tried what you posted above & couldn't believe what I found. I have two legal copies of XP...Pro & Home. I did a search of the CDs for "unattend.txt" & not only did I find a product key on each, but they were different than the ones I have. Cool! ;-)
EDIT: just tried it with my Win2K Pro CD. The unattend.txt is there, but it contains no product key. Next I'll try my Win98 & WinME CDs.
EDIT 2: my Win98SE CD has the unattend.txt but no product key. My WinME CD is an upgrade disc & has no unattend.txt file.
My question is this...if all XP CDs are a copy of a "Gold" master disc, would all of them contain the exact same unattend.txt file & therfore the same product key within that file?