Let's run through it.  The MBR (Master Boot Record) locates the partitions
on the hard disk.  Then points at the first ACTIVE primary partition.  Then
PBR (primary boot record) of the ACTIVE primary partition checks the
partition layout format, the FAT info if valid, then to the boot files.  3
of which exist for Win98.
Somewhere along the line during the PBRs job, the system cannot utilize the
boot files.  Most likely, after the FAT is checked.

If you have floppy or other media like CD inserted, remove from the PC to
eliminate other possibilities.
Dave