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I haven't tried it, but if you plug in the drive and boot from the Windows CD (bypassing the boot camp assistant)...I remember the drive appearing as an option for you to install XP on.

I know I was able to once install windows on a Mac Pro that had 4 HDDs in it and it targeted one whole HDD to install onto. If that's an option, you may be able to install it on a Mac Pro and then stick that drive into an enclosure.
 
I haven't tried it, but if you plug in the drive and boot from the Windows CD (bypassing the boot camp assistant)...I remember the drive appearing as an option for you to install XP on.

I know I was able to once install windows on a Mac Pro that had 4 HDDs in it and it targeted one whole HDD to install onto. If that's an option, you may be able to install it on a Mac Pro and then stick that drive into an enclosure.

For some reason a MP should be easy for them to get their hands on? I don't think it's possible for boot camp to work with an external drive.
 
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