XP uses NTFS instead of FAT for the format of the drive. Because of this, the boot diskette must have NTFSDOS instead of DOS on it. NTFSDOS, if you can find it, is bigger than one diskette and does not always work.
It would be easier to get a boot CD. BartPE makes such a CD. We have XP Recovery CD Maker that uses BartPE to make the CD. Not all XP computers have the correct files for BartPE so make sure you have an XP computer that has the correct files.
Or you can find boot CDs online for sale that are not too expensive.
Or maybe you have a friend that has such a CD.
Once you have a boot CD, put it in the CD drive, and start the computer. Because you are running off the operating system on the CD, you should be able to format C.