Dutch my wifes old computer has this problem all the time. well I just found out my memory wasnt quit seated all the way down. I would also disconnect the power supply (24pin) connector to the motherboard and reconnect it
. when I did that last one it would boot up again. However I dunno about you but ever since I reset the ram I havent had to reinstal anything as the computer starts like it should now instead of come on for a split second and then turn right back off.