I shut down my pc earlier came home went to turn on and i think i saw the power button light up for a half a second button shut off and now have no power at all.

Gateway all in one touch screen zx495. the fan was loud i cleaned it out the best i could without opening it. also we had a power outage a couple of weeks ago while i was on my pc. when it came on my pc was not letting me online and was giving security warnings the time and date were way off i beieve it said it was 1-1-10 and 12:00am. fixed that and a couple day later it got unplugged while on and it did the same time and date were wrong. but other then those things i dont have a clue to what happened. i have removed the back it is pretty dirty looking but i bought in march of 2010 so for 5 yrs its not as bad as i expected the air ways are not clogged. never been oprned til today