disk space used/free appears incorrect

In a windows 2000 configuration, my boot hard drive has a capacity of 127gb. Windows explorer shows 80.6gb used and 47.2gb free. When I total up all folders/files on this hard drive the total comes to 5.91 GB ACTUAL USAGE. Windows explorer show 80.6gb used. Why the huge discrepancy? Something is seriously out of sync. Any ideas????