Excellent, that will make this easy.
Head on over to
http://knoppix.com/
Download the knoppix 3.7 iso in your own language, which, if that is english, will be KNOPPIX_V3.7-2004-12-08-EN.iso
Burn the iso to a cd.
Boot from the cd.
Once knoppix has fully booted, open up a console and type "su" (without the quotes). If I remember right, this should pop you directly into root. If it asks for a password, type in "root" (without the quotes, you get the idea).
Once you are root, type in "qtparted". This will open up a nice program where you can change your partitions.
The win98 partition type will be FAT32. If you have more than one FAT32 partition, then stop right there and let me know.
If you are wanting to return the hard drive back to the standard windows set-up then simply delete all the other partitions, and resize the FAT32 partition to fill up the drive. Qtparted will give you a warning to back up your data before committing the changes. The back-up is a good idea, but I have never lost any data using qtparted and have not heard of anyone who has. I often don't back-up.
Once that is done, reboot, pull out the cd, and boot into windows.