In order to POST successfully you also need to have your RAM installed. It will never post with no RAM in the machine. It could very well be that your RAM is the issue here. If you have several sticks in your system try booting with just one installed. Try this in every single slot on your motherboard and then swap and do the same with your other stick. This will eliminate the possibility of a bad RAM stick since both are unlikely to be bad.
You may also want to ensure that your heatsink and fan unit are mounted properly. It's not likely, but I have seen some systems not boot because of small things like this that are often overlooked.
It may also be worth you having a look over this guide:http://www.tomshardware.co.uk/forum/261145-13-read-posting-boot-video-problems
It's a very good guide to basic boot issues etc. and may just help you identify any other issues it could be. You want to be sure its the motherboard before you shell out and buy a new one. Even if it takes you a while to go through all these at least your 100% its not something else! Hope this helps and good luck!