Red Light in processor tray, no boot, fans speed up

after installing a video card Radeon HD7950 my mac not boot only shows a red light on the processor tray and fan speeds loud , the power LED on the front is kept in white color and when press the button diagnostic motherboard, amber and 2 green turns on , already restart all, remove all devices PCI and extrnal cards and as usual, on one occasion the flashing red lED for a few moments. Already change thermal paste and remains unchanged. That could be?