The EVENTSENTRY_SVC.LOG file, located in the %SYSTEMROOT% directory (usually c:\winnt or c:\windows) is the debug log file of the EventSentry agent.
To reduce the size of this file set the "Debug Level" option in "Service Control" to "None" or "Low" and restart the EventSentry service.
The contents of this file are always cleared when the service is restarted.
Starting with version 2.50, there will be two log file (eventsentry_svc_1.log and eventsentry_svc_2.log) that will not exceed a combined size of ~50Mb.