Dying video cards can display a wide range of symptoms. I don't feel sufficiently versed to list them all, but here are some: CMOS beep code at startup No display, dark display, washed-out display, flickering display, lines in display, etc Crashes System unable to use higher resolutions/32bit color Extreme lag or crashes while using video-card intensive applications (like games) Extreme heat
Of course, all these symptoms can also result from other things, like a failing monitor, software issues, memory problems, etc. Perhaps it would be best if you described the problem, and we could go from there?
Can you connect to an external monitor? If no, its bad.