TNG service must run as SYSTEM.
You can check this under Task Manager (set to show all users).
Set the TNG service RECOVERY to restart service.
START -> CONTROL PANEL -> ADMINISTRATIVE TOOLS -> SERVICES ->
Right-click on TNG service and select PROPERTIES. Under the
RECOVERY tab set First Failure, Second Failure, Subsequent Failures
to RESTART THE SERVICE.
Restart the PC to enable the setting.
Check the Windows Events logs for clues why the service stopped.
Windows runs the services and it should point out why there is a problem.
See if there are any errors in the TNG logs that might influence the
running of the service. Logs is located in the date folder in
'C:\Program Files\Datatex\tng\logs'.