I have a acer extenas 5420 and it will not power up. I push the power button and it comes on but gos out. I have tryed to remove the battery and power supply, then hold down the power butten. then installing battery and power supply ( did not work ).all i did was install windows 7 and all drives; it worked fine for a few days but i truned it off and this happen when i turned it on. also i can hear the hard drive start and the cooling fan come on, but the light gos out.