Was the 80 gig drive set as one partition or as multiple partitions before?
If it was multiple and you only formatted C that would possibly explain why you only have 31 gig if that was the size of that partition.
Have you got a 98 boot disk ?
If you have you can use that to boot up with and use FDISK to see what the drive set up is and delete any extra partitions.
How did you format the 80 gig drive ?
If you used XP to do it and you did it in FAT 32 it will only format up to 32 gig.
If you reformat as NTFS then that would enable the whole drive to be seen.
If you definately want it as FAT 32 then you would have to use FDISK and format it in that as a FAT 32 drive, unless you split the drive into smaller than 32 gig partitions and formatted each partition using XP