not showing correct hard rive capacity

Hi,
I have a windows 2000 server. The hard drive is not showing the correct capacity. It should be 8 gig but it is showing 4 gig. When I goto the disk configuration it shows 8 gig being used but when I go to display it in my computer it shows the capacity as 4 gig. I really do not want to reformat the hard drive. I also ran chkdsk and it found no problems. Is there a reason for the hard drive to not show correct capacity? Thanks in Advance