The minimum requirements Microsoft lists are: a 233 MHz CPU (technically,
there *was* a 233 MHz P5), 64 MB of RAM (which was the maximum cacheable
memory on most of the P5 chipsets, except for the 430HX), and 1.5 GB of hard
disk space.
Whether XP would actually permit itself to be installed on such a system, I
have no idea. Whether a sane person would install XP on such a system, I
also don't know. (I doubt it, though.)
If you can tolerate the 32 MB download, you could try running the Upgrade
Advisor: