How many times have you seen this in a movie or TV series:
In order to destroy an electronical device (be it enemy computers, an evil robot, nanobots or whatever), the good guys cause an EMP (electro-magnetic pulse) to do this. In order to not to destroy their own computers and electronic devices they simply turn them off for the duration of the EMP, and then they just turn them back on, and everything is fine.
I have seen that many times.
The problem is that the device being turned on or off has no effect on the destructive force of the EMP. An EMP destroys electronics because the strong magnetic field creates large potential differences between the delicate conductors, creating electric arcs between them and consecuently burning them, effectively breaking the electronics. Simply switching the device off is in no way a protection against this. It doesn't have anything to do with the phenomenon.
Except in Hollywood, of course.