Cause: This generally occurs when your bootable floppy has an older version of the FDISK tool.
Solution: FDISK is a hard drive partitioning tool often used for preparing the hard drive before installing an OS. This tool is often bundled with the Windows CD, and is an essential part of the bootable floppy created using any Windows machine. If you have your original Windows 98 CD then boot the machine via it and then use the FDISK tool from the CD. Else you can also use the Ranish Partition Manager- a free tool and excellent at that too. Go to www.ranish.com/part to download it.