I would probably look at extending the ADLO/Bochs combination to implement whatever is missing for XP though. It may not be at all much. But then again, it may be months.
According to the bochs website XP is reported to work under bochs. If so then all that would be needed is an upgrade of the copy of bochs bios. That should get you all the necessary bios services.
I tried this probally a year or so ago but it breaks the IDE interface. Since at the time the new bios didn't really offer that much in the way of new features I didn't continue.
Fixing the IDE should be pretty simple. Diffing the ide routines to the current shows what Adam did to make them work.
-- Richard A. Smith