I'm currently not using windows, but you could try creating a BAT file (watchdog.bat) with the following:

shutdown -r -f -c "GPU card freeze"

Then configure your start.bat to look something like:

optiminer -s %POOL% -u %USER% -p %PASSWORD% -m 8080 --watchdog-timeout 30 --watchdog-cmd "watchdog.bat"

I found these links for reference on shutting down a mswindows computer:
https://technet.microsoft.com/en-us/library/bb491003.aspx

Let me know if this works.