The iMicro PS-IM400WH is a typical ultra low-end power supply that must be avoided at all cost. Using this kind of bargain power supply will give you lots of headache.
This “400 W” unit can only deliver around 280 W, with low efficiency, and these are not even the worse problems of it.
The problem with ultra low-end power supplies, and the iMicro PS-IM400WH is no exception, is that their voltages get easily outside the proper working range, and the noise and ripple levels are always above the maximum allowed. These two problems will, in the best case scenario, make your computer to work unstable (i.e., presenting random problems), and, in the worst case scenario, overload and even burn components from your PC.
In summary: stay away!