Is it the priv.edb and pub.edb that are that big, or is it the logs that are taking up the space? If its the logs, you can shutdown all of the services and delete all the EDB*.LOG files in both the EXCHSRVR\DSADATA and EXCHSRVR\MDBDATA directories (I would back them up instead of deleting them just in case.) Check out MS Q128325 for details.