|Your drive may be too large, find out what size it is and post that info.|
Your drive might be NTFS partitioned which DOS/Windows won't see but FDISK still should have if the above is not a problem.
Your drive may be defective. Use Bart's Disktool on it to see what the programs reports on the drive.
The drive could be jumpered wrong, double check against diagram on hard drive. My bet is too big for 98 or the drive is jumpered wrong.