Exactly what you said.

I had a Niveda graphics card installed in my Dimensions 3000 in order to be able to run the Sims 3. Over the past month it would crash during game play and the only way to recover the computer was to turn it off manually. Sometimes the colors would go completely crazy and the same thing: turn off the computer. I tried to fix it and it seemed to be working fine, but now when I try to turn the computer on, it goes from the boot up screen straight to a black screen. I can see the mouse and I can change the monitor settings, but it won't get past this.