Insert your Windows XP CD, and boot from it.
After it finishes loading the files, find a way to repair your Windows installation.
I think you can do that by pressing enter, which will go you to the installation screen (don't worry, it wont automaticly start installing).
I think that there will be an option asking you if you want to repair windows on the selected partion.
Select that option, and then let it do it work.
Your files won't be deleted (I guess
)
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