NTFS ?

no not in win98... only in NT may you convert to NTFS

The type of file system is determined by the partitioning, not formatting.
To change the file system type from FAT32 to NTFS you should use the
converters available in an OS such as W2K, or you should delete the
partition and create it from new. Note that if you create it as an NTFS
partition then Windows 9x will not be able to access it unless you provide
some third-party utilities.
--
Jeff Richards
MS MVP W95/W98

Win98 cannot use or even see an NTFS partition (but see
http://www.sysinternals.com/ntw2k/freeware/ntfswin98.shtml for a
product to let Win98 use NTFS partitions in a multi-boot environment).

If you're using WinXP, or something else that can handle NTFS, then
you can convert a FAT32 partition to NTFS. XP comes with a tool that
will do it, and there are third-party apps that can to it also.

The format command does not switch file systems, it formats a
partition in the file system for which it was created. FDISK can
delete existing partitions (losing all data) and create a new one in
any file system you choose. After creating it you format it, then it's
ready for use.

NTFS is for Win2000 and XP.  You can format to the NT
filing system if you have those operating systems.  Win98
does not recognize NTFS since it was made before the
advent of Win2000 and XP.  Win2000 and XP will recognize
FAT32 though.  NTFS is more efficient and provides better
security.  Bottom line..you have to have Win2000 or XP to
reformat to NTFS.