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The 'Dual Boot Installation with Windows 7 and XP' tutorial has been used by a lot of people, very likely +1000, and no errors or problems have been reported.
Just to make sure I understand your description.
You have Windows 7 installed on one partition of your 160GB HD, you made another partition to install XP on? Is this correct?
In the tutorial, you followed METHOD TWO: When Windows 7 is Installed First, correct?
What size is the Windows 7 partition?
What size is the XP partition?
Please fill out your system specs, this will help us to solve your problem.
You can down load SIW - System Information for Windows
to get all the information about your computer.