How to format C
Formatting C drive is fully described in this topic – how to format C (format a computer and install windows XP)
You can navigate to the link for more information’s.
Note: If you format C drive on your computer, you will loose all data stored in your Windows folder, My Documents folder, Program Files, and any custom settings applied to your windows installation.
Be sure to read the Should I format section, before your proceed.
Good luck (: