Hard Disk Optizing

I have a 10gb hard disk with one partation in a Windows 98 SE computer. Recently I am getting messages that I have run out of capacity. The useable space seems to be only 3.2gb instead of the full 10gb. How can I utilize the full 10 gb on this hard disk?
Is there a comatability problem in Win98SE that limits the size of hard disks that can be used?