I have exactly the same problem. Replaced memory. Tried different power supplies. When power is applied the board starts and everything (fan, external USB drive, SATA drive, etc.) for about 3 to 5 seconds. No video ever. Then everthing shuts off after one beep from the speaker port. Power button has no effect after that although I can repeat the whole process by cycling power completely off. The little green LED on the board remains lit showing that the board is detecting external power. I have tried everything including minimal configuration (no drive, no keyboard, no USB, only memory and video) but with same result. I am wondering whether the power supplies are all incorrect? The manual says TFX12V or SFX12V (page 43). Have the feeling that there is something really simple that I am forgetting. Have built many computers and several mini-ITX but this one has me stumped.