help please. dual booting trouble

[daverd]

i have ubuntu 8.4 on my computer but my girlfriend is haveing problems using some apps. i dont want to have to reload ubuntu onto my machine if i dont have to . but she wants me to put windows xp on it for her when i tried to add it two my second harddrive witch is blank it says it needs some room on the main for the mbr and i dont know what partion to resize in order to do this or if its even posible

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