Try
www.bootdisk.com, download the Win98 OEM boot disk and the updated fdisk, it's a little further down the page. Then, you can run the boot98.exe file to create the boot floppy. Once it's made, you can copy the new fdisk over to the floppy.
Finally, boot w/ the floppy, hitting CTRL+C or holding down the left shift key to get out of the startup sequence. Once you have a command prompt, run FDISK from the floppy to erase partitions.