Why does my power cut out when i turn my computer on?

i'll turn the computer on and then the power will flicker and the computer will turn off and the power will come back. the clock will come back on etc. even the fan across the room in a different outlet goes off then on. what does that sound like to you? the computer could be the problem? or wires in the plugs? circuit breaker wires? what steps can i take to check things before i have to spend a lot of money with an electrician?