Missing space on DATA volume...

I am running Nterprise Branch Office 2.0 with service pack 2 applied in
four offices on identical hardware. HP ML350 server with 1Gb RAM and a
147Gb SCSI drive.
One office shows right at 100GB used on the DATA volume. I can only
find about 36GB of data on the volume by doing a search on the folders.
I performed a purge and it still shows about 100GB used, 30Gb free, and
all reports still show only about 36 GB worth of actual files/data on
the volume.
How may I go about repairing the volume? GroupWise and RSync are both
active.

Thanks,
Tim Sullivan