The ProTop3 DB Monitor Windows service won't stay running

Follow these steps to resolve issues with ProTop like agents not starting, the ProTop3 DB Monitor service starting but stopping right away or you are getting "No Heartbeat" pages from the ProTop Portal.

Open the Windows Services app and stop the ProTop3 DB Monitor service.
Remove all the files from your PROTOPDIR\tmp folder; if you get errors about not being able to remove files, skip to step 4.
Start the ProTop3 DB Monitor service. This usually does the trick. If the service complains about files in use, other ProTop processes still hold onto some of those files, so go on to the next step.

Use process explorer to identify and kill processes holding on to files in your ProTop installation folder:

Open a command window with administrative privileges.
Start PROTOPDIR\ubin\procexp.
Use the search tool (binoculars icon) and search for your protop installation directory name, e.g., protop from c:\protop.
Using process explorer, kill any process (usually _progres.exe) you find in that search.
When all of the processes are gone, you should be able to remove any remaining files in PROTOPDIR\tmp.
Restart the ProTop3 DB Monitor service and verify it remains running.