How to re-format C drive with XP

First it is not possible to format C drive directly from explorer  if the OS already, it can only be formated via the boot from CD then try to instal window and at a stage you will be ask to partition your harddisk, and here is where the C drive will be formated.

Reboot, the press F8, to go to the bluescreen, then select the BIOS option look for boot function, and select the boot from CD.

Reboot, and it will boot from CD and follow the process to instal the window xp then.