These could be caused by numerous things and truly happen at any time. The damage they trigger is dependent on the power of the surge and can be anything from a blown fuse to totally frying the inside of your pc with accompanying smoke (as was reported in Darwin a couple of years in the past). In all cases investing in a proper surge protector is important. You'd be looking to invest about the $70 to $90 mark for a 5 to seven port protector. Some causes theft prevention system of electrical surges ...