Sigh...
killtask just ends the process of the program running. Killing explorer.exe will not crash your computer it will just end the process which results in your task bars disappearing along with all your icons and explorer windows. You can start the process up buy running explorer.exe
Neither scripts will crash your computer. Your computer will just reallocate memory to the processes cmd.exe and everything else will slow down. When your computer starts running out of memory Windows will stop the process that is creating the explorer windows.