Before I opened it and cleaned it , it was going into safe boot, and even upon disconnecting everything except power and video, it still went into safe boot. It was then I decided I might as well clean it anyways. I cleaned off all the dust inside, down to the heatsinks, graphics card and everything. Reapplied new thermal grease to the CPUs and put everything back together. Now when I boot it nothing shows up on my screen and the fan for the graphics card runs at full speed, though everything else sounds normal. I booted it with just the power and video cable attached and got the same result. Specs are as follows: Early 2006 Mac Pro 2.66 Dual Core Xeons (x2) 6GB Ram ATI x1900XT graphics card 250GB HDD Single super drive. Any help would be greatly appreciated!