If u get a laptop with an i386 folder on the c:\ I'd be tempted to copy that folder somewhere convenient like another partition (make a 5g or so d: if u need to, which could be handy for storing drivers and the like incase the person ever comes back to u, along with other things u install like free-avg or whatever). Then I'd try booting to something like a usb stick that has win98 startup or summit, and once at command prompt try: d:\i386\winnt32.exe (or .ex_ whichever it is)
Should work in theory.
a good a guide as any to make a bootable stick.
Another thing I thought of that I feel is legitimate, is to find an OEM pc/laptop with the i386 folder on it, and use nLite. iirc, nLite asks to be pointed to a legit XP folder, and I think the i386 one should do. Don't adjust any of the tweaks, and maybe it'll make a cd for u to burn
Ofc u'll only use it for the repair using a legit key
Legend has it, u copy the contents of a RETAIL XP install CD to a folder, then copy over the i386 folder from the OEM over the one in the retail copy. I'd guess u could just burn the contents of that folder then and forget nLite.