Yep (Parapunter); tried that (first BIOS boot via USB).
Some sort of (presumably error) message comes and goes in a nanosecond (impossible to read). XP splash screen comes and goes in half a second; then an invite to start in 'normal', 'safe' mode - and all the rest - all of which just start the cycle off again back to square one.
Lots of chat on the web (true, or not) about XP boot not being supported from USB (?) plus a whole variety of other negatives (??).