I think Partition Magic will allow you to convert from NTFS to FAT 32 (I think - never tried it). But why would you want to? FAT32 is a pretty good option for the typical home user. Why not just stay there and stop worrying about it?
Well - OK, perhaps you are running WinNT 4. In that case, keep your boot partion at FAT16, just in case you ever need to recover via DOS.