My computer monitor has a green cast to it and we tried another monitor and it was still green. Is there a setting somewhere that could have gotten change. We were exchanging monitors with another computer and when we hooked it up it had a green cast to it. We exchanged them back like they were but the green cast is still there.

If you swapped monitors around and the same Orig PC gives a green screen, have you tried checkign the graphics card?

Has the graphics card got two connectors?

I would try the above or try another graphics card in the PC.

I didn't know this until later, but my husband said when he made the switch that he didn't shut the computer down. Would that have anything to do with it?

Shutdown the machines and try again.

Also have you or can you swap the working Graphics/Video Card from the working one to the one with green screen.

Please tell me what are the makes and models of the PC's

No we haven't tried swapping cards. One is an HP Pavilion a820n and the other one is an eMachines W6509. Would their video cards be compatible?