My new build died!

I did it, I build a new computer! I was so proud, for a week and a half. It worked perfectly. And then suddenly, as if someone snuck up behind me with a sledgehammer, it was all gone. I started with a coolermaster cosmos s case, a mach 1 1,000w psu, 9800 GTX+, Amd Phenom 9850, 500GB Western Caviar HDD, cheap 18x Optical Drive, this motherboard: http://www.newegg.com/Product/Prod [...] 6813131224 4GB Patriot 240 pin 1066 ram. I spent ever penny I had on this, to the tune of about 1,300. It was working fine, but then in Vista control panel, it told me that I only had half of my Ram working. So I took out and reinserted both my sticks of ram, to find that when I powered it on, all the fans, fan controller, and lights work, but I get no signal from the VGA. I would believe that it would be the Video Card, but I also have no power to my mouse or keyboard. This lead me to the motherboard, which I replaced, but still had the same problem. I've tried this monitor on 2 computers, it is not the monitor. If anyone has ANY suggestions, PLEASE tell me.