Remember that WINDOWS is not running so that's not it. Unless you see a BIOS BOOT SCREEN all it means is the machine needs repair.
Try THE DEAD PC at google.com to start learning about PC repair.
A similar card notes 400 WATT power supply and another listed 500 WATTS. It is possible you didn't get the power supply upgraded and it failed. http://www.newegg.com/product/product.aspx?Item=N82E16814150433
One day i tried shutting down my computer by using the shut down option in windows 7. When i hit shut down only my monitors went blank and the rest of my computer was still working. I did a manual shut down by holding down the power button. Now when i try to turn on my computer my screen remains blank on both my monitors. I have tried switching monitors but still no luck. I have a Biostar Ati Raedon 4650 HD video card that i put in the day before and a 350 watt PSU. How can i fix this?