I had the same problem not to long back and i'll tell you it was a pain in the ass. I had a brand new mb, video card, power supply, ram, but had my 478 celeron 1.7 willamette, little did I know and contrary to what the sales guy said, it didn't work. I knew the cpu worked. I took back the mb to get a new one, and they tested it and they said the mb was bad. And even though the mb box said it supported 478, thats all it said. I tried powering it up and it still didnt work so i had to buy a newer 478 cpu. I thought a 478 celeron was a 478 celeron, intel sucks, but anyway if your saying its not the video card then i suggest taking the cpu and mb back up to where you bought it if it wasnt from online and have them test it. Im leaning towards the cpu.