Possible way round this. 32 bit xp is activated as it is now.so create a norton ghost image if it now to use later if needed (ghost image will be activated so no need to reactivate)
once you have the ghost image partition hard drive (if you wish to dual boot on one hdd)and ghoat your 32 bit image back onto 1st partition ,then install 64 bit xp on second partition this will write to the 32bit boot ini allowing dual boot
once this has installed take another ghost image of 32 bit xp so you can easily ghost your 32 bit xp to either a dual boot or none dual boot configuration