|You're only using the drive for 98? |
You need to remove the existing partitions, repartition, format and install 98. Check my # 13 here for details:
In addition to that, fdisk will probably ask about treating HPFS and NTFS partitions as large. Answer Y to that also. Any HPFS or NTFS partitions will show as non-dos partitions in fdisk, option 3.
Sometimes non-dos partitions can be hard to remove. If you have any problems download DELPART and use it to remove the partitions. (It'll fit on a floppy disk and you can run it from there.) It's an old dos utility. A google search will turn up a download link.