alot of the PC's i have access to are turned on at all times of the day, so i have to setup a few scheduled tasks to make sure its running. to stop more that one miner running at a time i have used the following batch file which checks for a the miner running before opening it again. you will need to change miner.exe to the name of the file name of the miner your running.
tasklist /FI "IMAGENAME eq miner.exe" 2>NUL | find /I /N "miner.exe">NUL
if "%ERRORLEVEL%"=="0" GOTO end
<Insert command to run miner here>
:end
hope this is useful to some one