Ed Bedatu said:
What is responsible for a solid yellow 2 and 4 lights on an Optiplex 960 at bootup?
"A possible graphics card fault has occurred"http://www.manualowl.com/m/Dell/OptiPlex-960/Manual/187365
Edit: an old post, I know, but this post was one of the first Google results I came across, and it didn't have an answer. So now that I found one, the next person that needs it won't need to dig as deep as me.