I just installed a new Gigabyte GA-H55M-UD2H motherboard with a intel core i5 650 processor. I can not get it to boot, not even to the bios screen. I have a 680w power supply, 500w required, 2 X 1 gb crucial 1033 MEMORY in the right DDR3 fit. What could be the problem? Power is received, system will power up, power all fans. cd drive works. Will acknowledge usb flash drive, but still no boot. All I can figure is that I improperly install something.  . This is my first build. Disconnect all components except the bare minimum to enter the BIOS.  Leave only motherboard, CPU, cpu fan, 1-RAM module, keyboard, PSU, monitor.  Your goal is to get to the BIOS & nothing else, then add optical drive, HDD, 2nd RAM CHIP, until you find the culprit.
Nice motherboard!
http://www.gigabyte.us/products/product-page.aspx?pid=3309#ovThanks that is what I did from reading an earlier post. Turned out to be my graphics card. Not sure if it is compatible, it should be but might required os installation first. Booted right up. It might also take disabling the onboard graphics first or INSTALLING the driver. MUST have been just the video output which was disabled by the graphics card. You didn't say you had a dedicated graphics card.  That motherboard has onboard VGA & DVI.  Usually, the dedicated card will automatically be seen as the 1st graphics device.  I just did this on a Biostar, when I added a dedicated card, after using the onboard for more than a year.  Onboard automatically disabled; it booted Windows & I installed new drivers.