I have a 2 dual 2.66 intel mac and wondering if 64 bit XP will run on it.

Technically it will however BootCamp in 10.5 seems to run smoother with the 32-bit version. But that also depends on how you plan to use it; some apps like pro-video editors have stability issues in BootCamp and 64-bit XP where many games seem to run better.

If you're after gaming performance then use 64 bit; pro app compatibility 32-bit.

I am pretty sure that Bootcamp only runs 32.