Are uninteruppted power supplies really needed for todays computers. I was reading up on them and decided i should get one for my computer. So got an apc 390 watt unit. However there are friends that i tell them they need one because the power in the area will flicker every now and then. I don't think they really believe me when i tell them they need them. So my question is are they really a neccesity for the sake of your computer or for the most part are they not necessary? Both of my friends just got new dell computers. Thanks.