Before you start, consult A Word of Caution on Windows Zip Utilities.
First, make sure that no user or script process is currently using the depot. (To guarantee this, you may wish to stop the AccuRev Server.) Move the physical contents of the depot with a backup/restore tool (e.g. tar, zip, xcopy /s). Then, let AccuRev know about the move:
accurev chslice -s <slice-number> -l <new-location>
(Use accurev show depots to determine the slice number of the depot.)