Install ME first on C: partition formatted FAT32. Then install XP on D: partition, formatted either NTFS or FAT32 (FAT32 if you want ME to be able to see D: drive).
XP will offer you choice of which OS to run at boot up... no need for any extra multiboot software (note, you should install oldest OS first, otherwise you have extra grief to achieve dual boot).
See also
http://www.techspot.com/articles/dualboot/index.shtml for a very good primer on the whole process.