Since any update of Dropbox client software will probably re-establish DbxSvc service to be started automatically, here is my solution to put it back to and keep it in disabled state automatically:
Create some folder (e.g. "C:\DbxSvcWatchDog"). Inside this folder create a batch file named "dbxsvcdisable.cmd" with the following contents:
@echo off
sc stop DbxSvc
sc config DbxSvc start= disabled
Right click file "dbxsvcdisable.cmd" and create a link to it inside the same folder. Rename this link to "dbxsvcdisable" (this is the link's name as shown within Windows Explorer; a "DIR" command at the command prompt will show the link's name to be "dbxsvcdisable.lnk").
Edit the properties of the link, set its execution mode to "minimized" and activate the "run as administrator" feature via the Advanced... button. The last step is important, because you need administrative rights to execute the script (which provokes an UAC message you have to confirm in order to allow execution).
Inside the folder create a second batch file (a watchdog that constitutes a wrapper around the stop script) named "dbxsvcwd.cmd" with the following contents:
@echo off
SETLOCAL ENABLEDELAYEDEXPANSION
for /f "tokens=3" %%i in ('sc qc DbxSvc ^| find "START_TYPE"') do (
if NOT "%%i"=="4" (
call dbxsvcdisable.lnk
)
)Right click file "dbxsvcwd.cmd" and create a link to it inside the same folder. Rename this link to "dbxsvcwd". Edit the properties of the link and set its execution mode to "minimized". Move this link file to the startup folder for all users (C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup).
Now every time Windows starts the wrapper is executed. It checks if the state of service DbxSvc is still set to disabled. If so nothing else happens. Only in the case that the service's state has changed from disabled to some other state (e.g. via an update of the dropbox client software), the stop script is run. You notice this via the UAC window you have to confirm for execution.
