I bought a Sapphire HD 3850 video card and a Stealth XStream 600W power supply. I put in the power supply and checked the system. All was working fine. I then put in the new video card and it worked for a little while and then the monitor went black. I put in the old graphics card and now the monitor is not working at all. It says no input. I hooked my computer to another monitor and receive the same no input message. I put my old power supply back in with my old video card and the monitor still has no input. I also connected the monitor directly to the original on the motherboard and it is still not working.