|Please describe the problem you are experiencing more detailed.|
If clean install is what you want, then you should make sure all important data on the OS partition is properly backed up.
From the other side, you can go with the Repair option which leaves your data intact, but won't clean any junk software (and similar) that may be present on your PC.
How to perform Win XP repair installation
Note: You may need to set the DVD drive as first boot device so as to boot from the CD.
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