I have the M4A785TD-V EVO AM3 Asus motherboard. When i first bought this computer i only bought 4GB of RAM since i was on a limited budget. A couple weeks ago I bought 8GB of RAM and i tried installing it 10 different ways and my motherboard has yet to recognize it. My computer doesnt even boot up. I did an RMA on the RAM thinking it was bad and the new RAM still doesnt work. I tried the RAM in my friends motherboard (he has the same board as me) and it still didnt work. I've looked into updating my BIOS. But all the BIOS update after my version have nothing do with RAM. I've read the motherboard manual multiple times and i can install a maximum of 16gb on my computer and yes i am running 64-bit windows 7 professional.
i have the same motherboard, but the micro version, i know the answer to your issue.
IT IS THE BIOS
maybe not the latest one, but an older version has info indicated the correction. I had upgraded to 8GB as well (i thought my old memory was bad) and the issue ended up that it was my MB and my MB got replaced, the replaced MB would not do anything (^^^^^^^^) so I backed off to my old 2GB modules, BAM it worked, booted to windows, flashed bios, shutdown and put in the new 4GB modules - worked like a charm
ASUS flash bios program from windows works just fine
put in a 2GB module and see if it boots up.
if it boots up, update your BIOS
put in 4 GB module and see if it boots up
if you see your OS - YAY!
if nothing, go back to 2GB and up the voltage and reinstall the 4GB - rinse and repeat as required