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How to Convert a Macintosh Hard Drive to Fat 32. Apple computers configure hard drives differently than Windows computers. Windows uses NTFS or FAT32 as their native file system while Apple uses HFS+.

In XP, there should be a tool that will convert FAT to NTFS. I think it's in Start -> Accessories -> System Tools; I'm not sure because if your partitions is already NTFS when you installed XP ...