</font color=blue>Your question is not correct. You failed to tell about your partitioning, drive and system installation configuration. Also the answer might be slightly different if you attempt to get rid of NTFS at all after dual or multiple boot.
Just as an example, I assume that C: is your WinXP system and boot partition, and you are going to get rid of your previous WinXP installation by formatting your C: partition.
Clarify, please, if my guessing is wrong.
The best way to format any partition/disk, not only system partition C: use the way described in the README.HTM file on the WinXP installation CD:
<font color=green>2.1 If You're Installing a New Copy (Clean Install)
If your computer has a blank hard disk or your current operating
system isn't supported, you need to start your computer by using the
Windows XP Professional CD. Some newer CD-ROM drives can start the
installation from the CD and automatically run the Windows XP Setup
Follow the Wizard.
When prompted to choose an installation type, select New Installation, and then click Next.
·Windows XP Professional can delete existing, create new partition and format a partition.
Select a File System. After formatted, exit from the installation process, or reset and reboot.