Disk Quota Report Incorrect Disk Usage

On the C Drive, the Quota Entries window reports two of the user entries
with incorrect disk usage. The BUILTIN\Administrators entry reports 275.2GB
in the Amount Used column. This is incorrect because the C Drive has 80GB
disk capacity. Also, another user entry reports 57GB on the C Drive. I
know this is incorrect because clicked the Delete button to see the files it
reports, then checked those folders reported; the disk usage is actually
22GB. What is going on?

How can one force Disk Quota to recalculate the volume?

I have Windows 2000 Professional SP4 will all the Windows Update and the
Indexing Service enabled Also, Norton SystemWorks 2003 is installed.

Thanks in advance