normally if you have to exchange files betweeen XP & Linux, the conventional way is to have a filesystem which is common for both (r/w by both) like FAT32. But now things are changing. Mint can read NTFS & there are programs for XP that can read ext3 filesystem. So its up to you... whether you want 3 partitions with one having XP the other Linux & the third common for both to share files (FAT32) OR with 2 partitions one for XP having ext2 IFS for reading ext3 FS & of course mint can read XP NTFS.
Don't fix it if it ain't broken, don't break it if you can't fix it -Husse