pls tell me if your bootloader prior to grub allowed you to boot into MS where it was on sda5 or have you made changes?
2) if no changes other than bootloader follow my tutorial on how to trick ms with the map command something like
title XP
root (hd0,4)
map (hd0,0) (hd0,4)
map (hd0,4) (hd0,0)
makeactive
chainloader +1
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