I am using a very small program (88 k) which dont need installation.
Download it from the following link and keep it in a separate folder because the program create by himself a file to save your settings.http://www.stopwatch-timer.com/xntimer.exe
Remark : after selecting the timer you wish to switch off your PC , check the lunch a file box & write in the blank line (one time only, it will be automatically saved) the following :
%windir%\system32\shutdown.exe -s -f -t 00
be carefull to keep space between -s and -f and -t and 00 (double zero)