If the parition is under 32 Gig, then XP can do it directly, possible from
the windows level. If not, then the XP recovery console, run from the XP
CDROM can do it.
If the partition is over 32 Gig, XP will refuse to partition it as FAT32.
However, many third-party tools can do that, and XP will then be happy to
use it.
I have used Partition Magic to reformat NTFS to FAT32.
Be aware that "reformat" = "lose all data" on the partition.
If you want to change format without losing data, then a tool like Partition
Magic should be able to do it. But, the user should always backup data,
before operating on paritions in this manner. Accidents happen.